Illumination device having a tapered light guide

ABSTRACT

This disclosure provides systems, methods and apparatus for illumination devices. In one aspect, an illumination device having a longitudinal axis includes a light source and a light guide. The light guide has a peripheral edge, a transmissive illumination surface, a center portion, and an upper surface. The transmissive illumination surface is oriented perpendicular to the longitudinal axis and disposed between the center portion and the peripheral edge. The upper surface is oriented relative to the illumination surface to define an angle α therebetween. In some implementations, the angle α can be greater than 15 degrees, for example.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/272,174, filed May 7, 2014, which is a continuation of U.S. patentapplication Ser. No. 13/563,377, filed Jul. 31, 2012, now U.S. Pat. No.8,721,149, which claims priority to U.S. patent application Ser. No.12/864,857, filed Jul. 27, 2010, entitled “THIN ILLUMINATION SYSTEM,”now U.S. Pat. No. 8,348,489, which is a national stage application ofInternational Patent Application No. PCT/US2009/000575, filed Jan. 29,2009, entitled “THIN ILLUMINATION SYSTEM,” which claims priority to U.S.Provisional Patent Application No. 61/024,814, filed Jan. 30, 2008,entitled “THIN ILLUMINATION SYSTEM,” all of which are hereinincorporated by reference in their entireties.

TECHNICAL FIELD

This disclosure relates to illumination devices.

DESCRIPTION OF THE RELATED TECHNOLOGY

The state of the conventional lighting fixtures used in commercialoverhead lighting applications around the world, from the lightingfixtures or luminaries routinely mounted overhead in traditional officeceilings to the many types and shapes of fixtures used in outdoor streetlighting, has not changed appreciably in a great many years. Standardlighting fixtures have remained typically large (24″×24″), thick(4″-10″), and weighty (7-30 lbs). The illumination they provide onsurfaces below them is often brightest directly underneath, falling offin brightness quickly as distance from the fixture's location increases.Even though a given lighting application may require illumination heldpredominately to a limited geometric area (for example, a table top orwork area), nearby viewers still receive unwanted glare when lookingupwards at the fixture's physical aperture. While some conventionalfixtures have been designed for limited-angle spotlighting purposes,they typically achieve net illumination efficiencies far lower thandesired from a modern energy conservation perspective. Some light, iswasted by misdirection outside the area of interest, and other light, bythe inefficiency the deliberate physical baffling added to block glare,which also adds significantly to the fixture's mechanical bulkiness.

A wide range of prior art has been associated with improvements in oneaspect or another of the various lighting characteristics of this broadclass of conventional lighting systems (for example, fluorescenttroffers and recessed quartz-halogen or metal halide down lightingcans). While modest gains have been made in luminaire efficiency,uniformity of illumination, and glare reduction, to mention a few, thelighting fixtures themselves have still remained as bulky and imposingas ever.

The net weight of conventional lighting fixtures is too heavy for moststandard commercial ceiling frameworks without costly and cumbersomemechanical reinforcements. The heaviest lighting fixtures in mostindustrial applications need be suspended from the building's structuralutility ceiling, rather than from its more convenient decorative one,unless the decorative one is reinforced substantially. Even in the caseof the lightest weight conventional fixtures, reinforcing guide wiresneed be added to provide the extra mechanical support.

Conventional recessed lighting fixtures are also quite thick, which addsto the overhead plenum space required above the decorative ceiling toaccommodate them, thereby reducing the effective ceiling height. Ceilingheight reduction is particularly an issue in high-rise buildings whereceiling height is already limited by the building's structural boundaryconditions.

Recently, commercial lighting fixtures utilizing assemblies of miniaturelight emitting diodes (LEDs) have started to appear in earlyapplications featuring lighter, more compact packaging. While this trendpromises still greater lighting fixture advantages over time, earlydevelopments have yet to realize the full potential.

One reason the early LED lighting fixtures have lagged in achieving thecompactness they promise is a consequence of their enormous brightnesscompared with that of the traditional light bulb alternatives. Lightemitted by LEDs is created in very small geometric regions, and as aresult, the associated brightness (i.e., lumens per square meter persolid angle in steradians) can be extremely hazardous to human viewwithout additional packaging structures added to block, restrict ordiffuse direct lines of view. One early solution to the LED's dangerousbrightness levels has been to hide them from view in lighting fixtures,whose light is reflected indirectly upwards off wall and ceilingsurfaces. While this approach prevents accidental view of the LED'sdirectly, the associated fixtures are as bulky as conventional ones.Another solution involves diffusing the LED light over a larger outputaperture. While this approach moderates aperture brightness infloodlighting applications, it does so at the expense of the fixture'sthickness, and while also increasing the fixture's propensity foroff-angle glare.

Looking at a bare LED emitter, even one combined with a reflector or alens, is a quite unpleasant experience, typified by temporary blindnessand a remnant image lasting minutes or longer. One of the most powerfulof today's newest commercial LED emitters generates about 300 lumens ina 2.1 mm×2.1 mm emitting region. This is a brightness of 20 millionCd/m² (nits). Such brightness appears more than 65,000 times as brightas the background brightness of the typical LCD display screens used inmodern desktop computer monitors. Such brightness also appears to be 200times brighter than the 18″ diameter aperture of commercial lightingfixtures using 250 W Hg arc lamps, which are already bright enough tocause viewers to see spots.

Modern LED light emitters require specialized lighting fixtures thatcapitalize on the LED's compactness potential, while providing a safeand desirable form of general illumination.

One of the more promising LED lighting adaptations involve a prior artLED illumination method, the so-called LED backlight. LED backlights arefinding more frequent use as the source of rear illumination for the LCDscreens used in large-format computer monitors and home televisions. Theemerging LED backlights involved are about 1″-2″ thick and spread lightfrom hundreds of internally hidden LED emitters uniformly over theirscreen area. By spreading and homogenizing the LED light emission, theLED backlight package thereby hides direct visibility of the otherwisedangerous brightness levels imposed by the bare LEDs themselves.

LED backlighting systems could be applied directly, for example,replacing the traditional 24″×24″×8″ fluorescent troffer in overheadoffice ceilings with significantly thinner and lighter weightalternatives.

As welcome as this possible LED lighting approach might be to commerciallighting use, the resulting fixture or luminaire is still a relativelythick and obtrusive one, veiling glare from its naturally wide angleemission remains an open issue, and beaming its output glow to limitedtask areas, is not provided. And while thinner than conventional lightbulb based lighting fixture, LED backlights are still too thick to beconveniently embedded within the body of typical building materials suchas ceiling tiles and wall board.

SUMMARY

It is, therefore, an object of this disclosure to provide a compact andslim-profile means of overhead LED illumination for commercial lightingapplications, for example, having a prescribed degree of angularcollimation in each of its two orthogonal output meridians and a squareor rectangular far field illumination pattern.

It is another object of this disclosure to provide a compact andslim-profile means of overhead LED illumination having its degree ofangular collimation modified in each of its two orthogonal outputmeridians by angle-spreading located in its output aperture thatmaintain the illumination system's rectangular far field illuminationpatterns.

It is a further object of this disclosure to provide a thinedge-emitting input light engine using a single LED emitter whose outputlight is collimated in one meridian and not in the other, working inconjunction with the input edge of a light guiding plate subsystem thatpreserves and transmits the collimated input light with out change inangular extent while collimating un-collimated input light, so that itsoutput light is collimated in both output meridians.

It is also an object of this disclosure to provide a thin edge-emittinginput light engine using an array of single LED emitters whose outputlight is collimated in one meridian and not in the other, working inconjunction with the input edge of a light guiding plate subsystem thatpreserves and transmits the collimated input light with out change inangular extent while collimating un-collimated input light, so that itsoutput light is collimated in both output meridians.

It is still another object of this disclosure to provide a thinedge-emitting input light engine using a single LED emitter whose outputlight is collimated in one meridian and not in the other, working inconjunction with the input edge of a tapered light guiding platesubsystem that preserves and transmits the collimated input light without change in angular extent while collimating un-collimated inputlight, so that its output light is collimated in both output meridians.

It is yet another object of this disclosure to provide a tapered lightguiding plate subsystem that receives input light along its input edgeand uses a specific arrangement of reflecting facets and associatedoptical films laminated to a plane face of the tapered plate so that thetapered light guide plate subsystem is able as to collectively extract,collimate and redirect a square or rectangular beam of output light intothe far field.

It is further an object of this disclosure to provide aone-dimensionally operating angle spreading lenticular lens array filmwhose parabolic lens shape enables unique far field characteristicscompared with prior art results.

It is still an additional object of this disclosure to provide for useof two orthogonally oriented one-dimensionally operating angle-spreadinglenticular array films having parabollically shaped lenticules able toconvert symmetrically collimated light input into either symmetricallyor asymmetrically widened output light having square or rectangular beamcross-section and the ability to create square or rectangularillumination patterns.

It is yet further an object of this disclosure to provide for the use oftapered light guiding plates whose cross-section has been extrudedlinearly forming square and rectangular tapered light guiding plateswith flat plane input edges.

It is still yet further an object of this disclosure to provide for theuse of tapered light guiding plates whose cross-section has beenextruded radially forming circular tapered light guiding plates havingcylindrical light input edges at the center of the circular plates.

It is yet an additional an object of this disclosure to provide for theuse of tapered light guiding plates whose cross-section has beenextruded both radially and linearly so as to form square and rectangulartapered light guiding plates having cylindrical light input edges at thecenter of the square or rectangular plates.

It is still one other object of this disclosure to apply lenticularfilmstrips to the input edge of light guiding plates for the purpose ofwidening the angle extent of an illumination system's output light inone meridian and not in the other.

It is still another object of this disclosure to apply geometricallyshaped portions of lenticular filmstrips to the input edge of lightguiding plates for the purpose of widening the angle extent only in alocal region of an illumination system as a means of improving nearfield brightness uniformity.

It is yet one other object of this disclosure to deploy thin-profileillumination systems with symmetrically and asymmetrically collimatedlight for the purpose of lighting a specific work task or work area.

It is additionally an object of this disclosure to deploy thin-profileillumination systems having oblique illumination beams withsymmetrically and asymmetrically collimated light for the purpose oflighting a specific wall mounted object, or for the purpose of providinga wash of light over a selected region of a wall.

It is yet an additional object of this disclosure to provide athin-profile illumination system whose aperture brightness has beenmoderated by spreading light over an enlarged area, while doing sowithout compromise in the sharpness of angular cutoff displayed by theilluminating beams that are produced.

It is a further object of this disclosure to provide a thin-profileillumination system whose aperture brightness has been moderated byspreading light over an enlarged area, while doing so without compromisein the square-ness or rectangularity of the field patterns that areproduced.

It is yet a further object of this disclosure to provide a thin-profileillumination system whose illumination remains largely within fixedsquare or rectangular angular beams as a means of reducing off-angleglare visible from below.

One innovative aspect of the subject matter described in this disclosurecan be implemented in an illumination device. The illumination deviceincludes a light guide and a light source. The light guide also includesa peripheral edge disposed about a longitudinal axis of the device, acenter portion having a light entry surface through which light emittedfrom the light source propagates into the light guide, a transmissiveillumination surface oriented perpendicular to the longitudinal axis anddisposed between the center portion and the peripheral edge, and anupper surface. The upper surface is disposed between the center portionand the peripheral edge and oriented relative to the illuminationsurface to define an angle α therebetween. The angle α is less than 15degrees.

In some aspects, the device can also include a reflective surfacedisposed adjacent to at least a portion of the upper surface to reflectlight toward the illumination surface. The reflective surface caninclude a reflective coating disposed over at least a portion of theupper surface or a prism-like ejection film, for example. The reflectivesurface can be separated from the light guide by a material having anindex of refraction less than an index of refraction of the light guide.In some aspects, at least a portion of the upper surface includes areflective surface. The angle α can be greater than 2 degrees and lessthan 8 degrees.

In some aspects, the device can also include an optical coupler disposedin an optical path between the light source and the light guide entrysurface. The optical coupler can be configured to receive light from thelight source and direct light into the light guide through the lightentry surface and can be a curved reflector. In some aspects, the lightsource can include at least one light emitting diode. For example, thelight source can include a plurality of light emitting diodes angularlyoffset from one another about the longitudinal axis. In some aspects,the light entry surface can be disposed around the longitudinal axis andfacing the longitudinal axis. Each light emitting diode can include alight emitting surface that is oriented to provide light through thelight entry surface into the light guide in a radial direction relativeto the longitudinal axis of the device.

In some aspects, the device can include an optical conditioner, forexample, a lenticular structure, disposed below the illumination surfacesuch that the illumination surface is between the optical conditionerand the upper surface. In some aspects, the light entry surface can beformed by a recess in the upper surface of the light guide.

In some aspects, the device can include an electrical coupling having atleast two separate electrical connections for connecting theillumination device to a power source and an electronics chassisdisposed between and electrically connecting the electrical coupling andthe light source. In some aspects, the electronics chassis can include aheat transfer structure thermally coupled to the light source todissipate heat from the light source, for example, a heat transferstructure disposed between the electronics chassis and the light guide.In some aspects, the electronics chassis has a maximum radial dimensionthat is less than a maximum radial dimension of the light guide. In someaspects, a chandelier can include the device and can include a connectorthat is offset on the longitudinal axis from the light source andelectrically coupled to the light source. The chandelier can include amounting plate disposed between the light source and the electricalcoupling and configured to mechanically couple the chandelier to a fixedstructure.

Another innovative aspect of the subject matter described in thisdisclosure can be implemented in a method of manufacturing anillumination device. The method includes forming a transparent structureincluding a tapered upper surface and a lower surface, and polishing thelower surface of the transparent structure to reduce a longitudinaldimension between the lower surface and the upper surface. A peripheraledge of the transparent structure between the upper surface and thelower surface after polishing defines an angle α greater than 1 degreeand less than 8 degrees.

In some aspects, the transparent structure can have a maximum radialdimension that is less than or equal to 4 inches. Forming thetransparent structure can include providing a substrate having a surfaceto support a tapered surface of the transparent structure. In someaspects, the method can include forming a light entry surface in acenter portion of the transparent structure and positioning a lightsource near the center portion of the transparent structure. In someaspects, positioning a light source near the center portion of thetransparent structure can include positioning the light source relativeto the transparent structure such that light emitted from the lightsource is received into the transparent structure through the lightentry surface and propagates in a radial direction from the light sourcetoward the periphery of the transparent structure.

Yet another innovative aspect of the subject matter described in thisdisclosure can be implemented in a method of installing a lightingdevice within a lighting fixture having an opening and an electricalconnection opposite to the opening and having a minimum radialdimension. The method includes providing a device including a lightguide and an electrical coupling. The light guide has a maximum radialdimension and has an illumination surface configured to emit light fromthe light guide, and an upper surface configured to reflect lightpropagating in the light guide toward the illumination surface. Theillumination surface and the upper surface meet at the peripheral edgeof the light guide defining an angle α between the illumination surfaceand the upper surface. The angle α is less than 15 degrees, for example,between 2 degrees and 8 degrees. The method also includes coupling theelectrical coupling of the device to the electrical connection of thelighting fixture.

In some aspects, the maximum radial dimension of the light guide can beless than the minimum radial dimension of the opening. In some aspects,the maximum radial dimension of the light guide can be greater than theminimum radial dimension of the opening.

Details of one or more implementations of the subject matter describedin this specification are set forth in the accompanying drawings and thedescription below. Other features, aspects, and advantages will becomeapparent from the description, the drawings, and the claims. Note thatthe relative dimensions of the following figures may not be drawn toscale.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates a perspective view of a thin profile illuminationsystem containing two interconnected subcomponents, an edge-emittinglight bar input engine using a single LED emitter and a light guideplate that outputs a beam of square or rectangular collimated light fromone plate surface.

FIG. 1B contains an exploded view of the illumination system illustratedin the perspective view of FIG. 1A.

FIG. 1C provides an additional degree of explosion for the illuminationsystem illustrated in FIG. 1B, adding perspective views of light outputfrom the edge-emitting input bar and of the light output from the systemas a whole.

FIG. 1D contains a perspective view of the illumination systemillustrated in FIG. 1A, with the addition of two angle-spreading lenssheets beneath the lighting guiding plate to process the outgoing beamprofile in one or both output meridians.

FIG. 2A illustrates a perspective view of a thin profile illuminationsystem segment containing two interconnected subcomponents, one anedge-emitting input engine using a single LED emitter as input and acorrespondingly single angle-transforming reflector as output, placed inconjunction with a rectangular version of the general light guide plateillustrated in FIG. 1A, that outputs a square or rectangular beam ofcollimated light from one plate surface as shown.

FIG. 2B illustrates a linear array of four thin profile illuminationsystem segments as shown in FIG. 2A.

FIG. 2C illustrates a perspective view of a thin profile illuminationsystem containing two interconnected subcomponents, an edge-emittingarray-type input engine using a multiplicity of LED emitters as inputand a multiplicity of angle-transforming reflectors as output, placed inconjunction with the same light guide plate illustrated in FIG. 1A thatoutputs a square or rectangular beam of collimated light from one platesurface as shown.

FIG. 2D provides an exploded perspective view of the output edge of theedge-emitting array-type input engine illustrated in FIG. 2A, includinga perspective representation of the engine's output light collimated inone meridian, and not in the other.

FIG. 2E contains the illumination system illustrated in FIG. 2A, withthe addition of two angle-spreading lens sheets beneath the lightingguiding plate to process the outgoing beam profile in one or both outputmeridians.

FIG. 3A illustrates a perspective view of a thin profile illuminationsystem containing two interconnected subcomponents, a taperededge-emitting light bar input engine using a single LED emitter and atapered light guide plate that outputs a beam of square or rectangularcollimated light from one plate surface.

FIG. 3B contains an exploded view of the illumination system illustratedin the perspective view of FIG. 3A.

FIG. 3C contains an exploded perspective view of the LED emitter, therectangular angle-transforming reflector, and the input aperture of thetapered edge-emitting light bar input engine.

FIG. 3D provides an exploded perspective view isolating on therectangular angle-transforming reflector, and the input aperture of thetapered edge-emitting light bar input engine, including a light coneinvolved.

FIG. 3E illustrates in exploded schematic cross-section the relationshipbetween the elements shown in FIG. 3D, including the simulated angularlight distributions developed in between them.

FIG. 4 provides a top view of the thin-profile illumination system ofFIG. 3A illustrating the dimensions and their relations to each other.

FIG. 5A illustrates in schematic cross-section the side view of atapered light guide pipe or plate, showing the corresponding angular farfield profiles of both input and output light beams.

FIG. 5B provides graphic profiles of the associated near field spatialuniformity developed on the tilted topside output face of the taperedlight guide of FIG. 5A.

FIG. 5C provides graphic profiles of the associated near field spatialuniformity developed on the flat bottom side output face of the taperedlight guide of FIG. 5A.

FIG. 6A illustrates the optical paths taken by a single paraxial testray undergoing total internal reflection inside a tapered light guide.

FIG. 6B illustrates the optical paths taken by a single paraxial testray undergoing total internal reflection inside a tapered light guide,choosing a slightly different start trajectory than the one shown inFIG. 6A.

FIG. 7A shows the effect on light extraction by adding a tiltedreflecting plane in air just above the tilted surface of the taperedlight guide illustrated in FIG. 5A.

FIG. 7B shows the effect on light extraction by adding a flat reflectingplane in air just below the flat surface plane of the tapered lightguide illustrated in FIG. 5A.

FIG. 7C shows the effect on light extraction by adding a tiltedreflecting plane that is optically coupled to the tilted surface of thetapered light guide illustrated in FIG. 5A.

FIG. 8A is a perspective view illustrating the single LED light emitterserving as the input portion of the double collimating lightdistributing engine examples of FIGS. 3A-3B and 4, as seen from itsoutput edge for the special case where its light extracting prismsfacets have collapsed to the unstructured form of a smooth mirror plane.

FIG. 8B provides a topside view of the edge-emitting LED light emitterof FIG. 8A, showing the obliquely directed far field beam cross-sectionthat results.

FIG. 8C provides a front view illustrating the light beam cross-sectionthat is emitted from the output edge of the system of FIG. 8B.

FIG. 8D illustrates the LED light emitter of FIGS. 8A-8C in a topsideperspective view showing the highly asymmetric nature of its obliquelydirected output illumination.

FIG. 9 illustrates the side cross-section of a tapered light guidingpipe (or plate) whose tilted (taper) plane is modified to include anoptical film stack having two different dielectric layers and a planemirror, also containing a superimposed simulation of the extractedoutput light's angular cross section.

FIG. 10 provides a graph detailing the quantitative relationship betweenthe angle of light extraction and the prevailing refractive indicescausing it.

FIG. 11A illustrates optical behavior in the side cross-section of atapered light guide structure similar to that of FIG. 9, but having aprismatic mirror plane composed of more steeply tilted mirror sections.

FIG. 11B provides a magnified side cross-section of a portion of theprismatic mirror plane of FIG. 11A.

FIG. 11C illustrates in schematic cross-section, the results of anoptical ray-trace simulation of light transmission within the taperedlight guiding structure of FIGS. 11A and 11B.

FIG. 12A provides an exploded perspective view of the edge-emittinginput engine that is a part of the illumination system of FIGS. 3A and4.

FIG. 12B provides a top view of the edge-emitting input engine that is apart of the illumination system of FIGS. 3A and 4, illustrating thecollimated output beams that are produced both just inside the lightguiding pipe comprising it, and as output in air.

FIG. 12C is a perspective view showing the edge-emitting output apertureof the edge-emitting input engine described in FIG. 12A showing aperspective view of the output emission that is well-collimated alongthe edge of the engine and significantly wider angled in the orthogonalmeridian.

FIG. 12D provides yet another perspective view of the engine of FIG.12A, this one containing a visualization of its coarse near-fieldspatial uniformity.

FIG. 12E illustrates still another perspective view of the engine ofFIG. 12A containing a visualization of its improved near uniformityassociated with its higher density of light extracting prism facets.

FIG. 12F represents the light distribution shown in FIG. 12D occurringon the output edge face of the input engine of FIG. 12A, when its lightextracting prism facet spacing is relatively large.

FIG. 12G illustrates the light distribution shown in FIG. 12F occurringon the output edge face of the input engine of FIG. 12A, when its lightextracting prism facet spacing has been reduced, but is still visible tohuman vision.

FIG. 12H illustrates the light distribution occurring on the output edgeface of the input engine of FIG. 12A, when the spacing of its lightextracting prism facets has been reduced, to dimensions not visible tohuman vision.

FIG. 13A is a perspective view showing the adverse effect a verynarrow-angle input source of light has on near field spatial uniformityalong the length of the engine's output edge.

FIG. 13B is a perspective view showing the beneficial effects awider-angle source of input light has on the near field spatialuniformity along the length of the engine's output edge.

FIG. 13C is a perspective view showing the adverse effects on near fieldspatial uniformity along the length of the engine's output edge whenusing an input source distribution with too large an angular range.

FIG. 14A is a graphic representation of one particularly narrow-anglelight distribution provided as input to the light guiding pipe of theedge-emitting input engine of FIG. 12A.

FIG. 14B is a graphic representation of a slightly wider narrow-anglelight distribution provided as input to the light guiding pipe of theedge-emitting input engine of FIG. 12A.

FIG. 14C is a graphic representation of an appropriately wide-anglelight distribution provided as input to the light guiding pipe of theedge-emitting input engine of FIG. 12A.

FIG. 14D is a graphic representation of too wide an angular lightdistribution provided as input to the light guiding pipe of theedge-emitting input engine of FIG. 12A.

FIG. 15 provides four comparative graphics plots of the input enginesnear field spatial uniformity as a function of distance from the inputaperture of the light guiding pipe involved, each corresponding to theinput light distributions of FIGS. 14A-14D.

FIG. 16A provides a perspective view of the dimensional relationsexistent between a thin-profile single-emitter tapered light guidingillumination system, in its single-emitter form of FIG. 3A, elevatedabove a far field surface area to be illuminated.

FIG. 16B provides a magnified perspective view of the tapered lightguiding illumination system as is shown in FIG. 16A.

FIG. 17 is a graphic representation of the far field illuminationpattern made on the surface illuminated in the perspective view of FIG.16A.

FIG. 18 is a graphic representation of a set of differently tilted farfield beam cross-sections generated by the illumination system of FIG.16A in response to five slightly different choices of facet angleswithin the prisms applied to the surface of its tapered light guidingplate.

FIG. 19 is a graphic representation showing nine different far fieldbeam cross-sections to demonstrate the +60 degree to −60 degree range ofbeam directions that are accessible by means of varying internal lightredirecting prism angles within the thin-profile light guidingillumination system's plate.

FIG. 20 contains a graph of prismatic facet angles within lightextraction and turning film versus the far field beam-point angle itcreates, for the thin-profile light guiding illumination system of FIG.3A.

FIG. 21 is a side cross-section illustrating the computer ray-tracesimulated far field angle spreading behavior of a prior art form of bulkscattering-type diffusing sheet applied in the output aperture of thethin-profile light guiding illumination system of FIG. 3A.

FIG. 22A represents a schematic cross-sectional side view of a prior artform of a cylindrical lens array film containing spherically shaped lenselements known as a lenticular diffuser.

FIG. 22B provides a perspective view of the cross-sectional lenticularstructure shown in FIG. 22A.

FIG. 22C provides a topographic schematic perspective view of thepebbled surface morphology of a prior art angle spreading diffuser filmstructure containing mathematically developed two-dimensionaldistributions of micro-sized lens elements.

FIG. 23A shows the far field beam cross section that results when +/−5degree×+/−5 degree collimated light as from the light emitting system ofFIG. 3A is applied to the plane side of a lenticular lens sheet havingspherically shaped lenticular elements.

FIG. 23B shows the far field beam cross section that results when +/−5degree×+/−5 degree collimated light as from the light emitting system ofFIG. 3A is applied to the lens side of a lenticular lens sheet havingspherically shaped lenticular elements.

FIG. 24A provides perspective view of a lenticular lens sheet structurehaving parabollically shaped lenticular elements.

FIG. 24B shows the round-bottomed far field beam cross section thatresults when +/−5 degree×+/−5 degree collimated light as from the lightemitting system of FIG. 3A is applied to the plane side of a lenticularlens sheet having parabollically shaped lenticular elements with arelatively shallow sag.

FIG. 24C shows the flat-bottomed far field beam cross section thatresults when +/−5 degree×+/−5 degree collimated light as from the lightemitting system of FIG. 3A is applied to the lens side of a lenticularlens sheet having parabollically shaped lenticular elements with arelatively shallow sag.

FIG. 24D shows the wider-angled round-bottomed far field beam crosssection with satellite wings that results when +/−5 degree×+/−5 degreecollimated light as from the light emitting system of FIG. 3A is appliedto the plane side of a lenticular lens sheet having parabollicallyshaped lenticular elements with a moderately deep sag.

FIG. 24E shows the wide-angle flat-bottomed far field beam cross sectionthat results when +/−5 degree×+/−5 degree collimated light as from thelight emitting system of FIG. 3A is applied to the lens side of alenticular lens sheet having parabollically shaped lenticular elementswith a moderately deep sag.

FIG. 24F shows the wide angle tri-modal far field beam cross sectionthat results when +/−5 degree×+/−5 degree collimated light as from thelight emitting system of FIG. 3A is applied to the plane side of alenticular lens sheet having parabollically shaped lenticular elementswith a very deep sag.

FIG. 24G shows the very wide angle far field beam cross section thatresults when +/−5 degree×+/−5 degree collimated light as from the lightemitting system of FIG. 3A is applied to the lens side of a lenticularlens sheet having parabollically shaped lenticular elements with a verydeep sag.

FIG. 25 is a graph summarizing the best mode geometric relationshipfound to exist between total far field angle and the paraboliclenticular peak-to-base ratios between 0.1 and 1.0, for lenticulardiffuser sheets.

FIG. 26 is a perspective view of the collimated thin-profileillumination system as depicted in FIG. 3A now containing a singleparabolic-type lenticular angle-spreading sheet below its outputaperture, the lenticular axes running parallel to the illuminator'sy-axis oriented input edge.

FIG. 27 contains a computer simulation of the rectangular far field beampattern produced by the illumination system of FIG. 26 on an 1800mm×1800 mm illumination surface from a height of 1500 mm; therectangular pattern stretched asymmetrically +/−30-degree along thesystem's x-axis.

FIG. 28 shows a perspective view of the collimated thin-profileillumination system as depicted in FIG. 3A containing two orthogonallyoriented parabolic-type lenticular angle-spreading sheets below itsoutput aperture, the lenticular axis of one sheet running parallel tothe illuminator's y-axis oriented input edge, and the lenticular axis ofthe other, running parallel to the illuminator's x-axis.

FIG. 29A contains a computer simulation of the square far field beampattern produced by the illumination system of FIG. 28 on an 1800mm×1800 mm illumination surface from a height of 1500 mm, the squarepattern symmetrically disposed +/−30 degrees along both the system's xand y axes.

FIG. 29B contains a computer simulation of the tighter square far fieldbeam pattern produced by the illumination system of FIG. 28 on an 1800mm×1800 mm illumination surface from a height of 1500 mm, the tightersquare pattern symmetrically disposed +/−15 degrees along both thesystem's x and y axes.

FIG. 30A provides an exploded top perspective view of one example of afully configured light engine implementation based on the functionalillustrations of FIGS. 1A-1D, 3A-3E, 4, 16A-16B, 26, and 28.

FIG. 30B provides a magnified perspective view of the coupling regionexistent between a commercial LED emitter that can be used, thecorresponding square or rectangular reflector and a tapered lightguiding bar with light extraction film.

FIG. 30C provides a perspective view of the completely assembled form ofthe fully-configured light engine implementation shown in explodeddetail in FIG. 30A.

FIG. 30D illustrates a related geometric form in which metal coatedfacetted layer may be replaced by a plane reflector and a separatefacetted light extraction element placed just beyond the front face ofpipe (facet vertices facing towards the pipe surface).

FIG. 30E is a perspective view showing the variation of FIG. 30D appliedto light guiding plate.

FIG. 31A provides an exploded top perspective view of a practical singleemitter segment following FIG. 2A for a fully configured multi-emitterlight engine based on a reflector-based means of input to a lightguiding plate.

FIG. 31B is a perspective view of the assembled version of the practicallight engine example shown exploded in FIG. 31A.

FIG. 31C is a schematic top view providing a clearer description of theunderlying geometrical relationships that are involved in matching LEDemitter, reflector and light guiding plate.

FIG. 32A illustrates a perspective view of a multi-emitter thinillumination system as was generalized in FIGS. 2A-2E and FIGS. 31A-31Cshown without top reflector to reveal internal details.

FIG. 32B is illustrates a perspective view of the system in FIG. 30A,with top reflector added, also showing the system's down directed farfield output beam profile.

FIG. 33A shows a topside perspective view of two side-by-sidedown-lighting engine segments of emitter-reflector-light guiding platethin illumination system variation illustrated in FIG. 31B.

FIG. 33B shows a topside perspective view of two in-line down-lightingtwo-engine segments of the emitter-reflector-light guiding plate thinillumination system variation illustrated in FIG. 31B.

FIG. 33C shows a topside perspective view of two counter-posedtwo-engine segments of the emitter-reflector-light guiding plate thinillumination system variation illustrated in FIG. 31B.

FIG. 34A is a schematic perspective illustrating execution of the globalboundary condition for linear extrusion of the tapered light guidingplates introduced in the above examples.

FIG. 34B shows in schematic perspective that the linear boundarycondition of FIG. 34A also forms the linearly extruded facetted lightextraction films as were shown in the above examples.

FIG. 34C illustrates in schematic perspective a basic execution of theradially constrained extrusion to form disk-type tapered light guidingplates.

FIG. 34D shows in schematic perspective the circular taperedcross-section light guiding plate that results from executing the radialextrusion illustrated in FIG. 34C.

FIG. 34E is a schematic perspective view illustrating the correspondingradial extrusion process for facetted cross-section sweeping about anaxis line and circular guide path to form a radially facetted lightextraction film.

FIG. 34F is a topside schematic perspective illustrating the radiallight extracting film that results from executing the radial extrusionillustrated in FIG. 34E.

FIG. 35A is a cross-sectional perspective view illustrating radiallyfacetted light extracting film of FIG. 34E and circular light guidingplate of FIG. 34D combined.

FIG. 35B is a cross-sectional perspective view illustrating the internaldetails of one example of a practical combination of illustrative LEDemitter (as in FIG. 31A) with radial light guiding system of FIG. 35A.

FIG. 35C is a magnified view of the cross-section of FIG. 35B showingfiner details of the light input region of this illustrative radial formof the thin emitter-reflector-light guiding plate illumination system.

FIG. 35D shows a cross-sectional view of an example illumination deviceincluding a tapered light guide.

FIG. 35E shows a cross-sectional view of an example illumination deviceincluding the tapered light guide of FIG. 35D.

FIG. 35F shows a cross-sectional view of an example illumination deviceincluding the tapered light guide of FIGS. 35D and 35E.

FIG. 36A is a partial cross-sectional perspective view revealinginternal details of the thin emitter-reflector-light guiding plateillumination system of FIG. 35A, but with an example of a radialheat-extracting element useful in such configurations.

FIG. 36B is a schematic perspective view of the illustrative lightengine implementation represented in FIG. 36A, without thecross-sectional detail of FIG. 36A, and in a down-lighting orientation.

FIG. 36C is a schematic perspective view similar to that of FIG. 36Bshowing the illustrative light engine implementation of FIGS. 35A-35Cand 36A-36B and it's intrinsically well-collimated far-field outputillumination.

FIG. 36D is an exploded perspective view of the light engine representedin FIG. 36B, adding parabolic lenticular film sheets and a circularframe to retain them.

FIG. 36E shows the unexploded view of the thin system of FIG. 36D.

FIG. 36F is a schematic perspective view similar to that of FIG. 36C butshowing the asymmetrically widened far field output illumination of thethin illumination system shown in FIG. 36E.

FIG. 36G shows the illustrative far field beam pattern from the thinillumination of FIG. 36F placed at a 1500 mm height above the 1800mm×1800 mm surface to be illuminated.

FIG. 37A is a schematic perspective view illustrating the thin profilelight engine example of FIG. 36E configured as screw-in style lightbulb.

FIG. 37B shows a perspective view of an example illumination deviceincluding a heat extracting element, an electronics frame, and a lightguide having a polygonal cross-sectional shape.

FIG. 37C shows a perspective view of an example illumination deviceincluding the heat extracting element of FIG. 37B, the electronicschassis of FIG. 37B, and a light guide having a curvilinearcross-sectional shape.

FIG. 37D shows a side view of the example illumination device of FIG.37H illustrated with an example light fixture.

FIG. 37E shows a perspective view of an example illumination device 5000c including the heat extracting element 2600 of FIG. 37B, theelectronics chassis 2701 of FIG. 37B, and a light guide 2101 having asize and shape that matches the light guide 2101.

FIG. 37F shows a side view of the example illumination device of FIG.37E illustrated with the example light fixture of FIG. 35D.

FIG. 37G shows a side view of an example illumination device illustratedwith an example light fixture.

FIG. 38A is a schematic perspective view of a square truncation of theradially constrained light guiding plate extrusion illustration shownpreviously in FIG. 34C.

FIG. 38B is magnified section view of the complete schematic perspectiveprovided in FIG. 38A, better illustrating the significance ofedge-thickening defects caused by premature truncation.

FIG. 39A illustrates a radially and linearly constrained extrusion withfive prototype taper cross-sections, swept in a 90-degree radial arcsegment about an axis line running parallel to system's Z-axis.

FIG. 39B is a perspective view illustrating the extrusive combination offour of the 90-degree segments as developed in FIG. 39A.

FIG. 39C is a perspective view, similar to that of FIG. 34D, butillustrating the quad-sectioned square tapered light guiding plate thatresults from the radially and linear constrained extrusion of FIG. 39C.

FIG. 39D is a perspective view of a thin square light engine form thatuses a square lighting guiding plate, and an otherwise similar internalarrangement to that of the circular light engine example shown in FIG.36E.

FIG. 40A shows a perspective view of another implementation of thesingle-emitter form of the thin illumination system 1 deploying atapered light guiding pipe system as its input engine cross-coupled witha tapered light guiding plate system using a plane top mirror.

FIG. 40B is a side cross-sectional view of FIG. 40A.

FIG. 40C is a perspective view of the illumination system of FIGS.40A-40B showing the collimated nature of the obliquely directed farfield output beam the system produces.

FIG. 41A is a side elevation showing the illumination system of FIGS.40A-40C mounted 10 feet above ground level and a horizontal distance of3 feet from a vertical wall surface to be illuminated.

FIG. 41B shows a front view of an illuminated wall surface and the beampattern made by illumination system 1 of FIG. 41A.

FIG. 42 is a perspective view of an illumination system similar to thatof FIG. 40C, but including a one-dimensional angle-spreading lenticularfilmstrip on the input-edge the system's tapered light guiding plate towiden the outgoing beam's horizontal angular extent.

FIG. 43A illustrates the side elevation of a wall and floor includingthe illumination system of FIG. 42.

FIG. 43B shows a front view of the wall surface illuminated using theillumination system of FIG. 42, including the resulting beam pattern.

FIG. 44 is a side view of a thin profile illumination systemimplementation based on the illumination systems of FIGS. 40A-40C, 41A,42 and 43A combined with an external tilt mirror.

FIG. 45A is a side elevation showing the tilted-mirror illuminationsystem of FIG. 44 for a 12-degree tilt mounted 10 feet above groundlevel and positioned 3 feet from the vertical wall surface to beilluminated.

FIG. 45B shows a front view wall surface illuminated by the 12-degreetilted mirror illumination system of FIG. 44 and its associated beampattern.

FIG. 46A is a side elevation identical to FIG. 45A, but for the case ofa 16-degree mirror tilt.

FIG. 46B shows a front view wall surface illuminated by the 16-degreetilted mirror illumination system of FIG. 46A and its associated beampattern.

FIG. 47 is a perspective view of the corner of a room, showing its twowalls, a floor, and a framed painting illuminated obliquely by thethin-profile tilted mirror illumination system of FIGS. 44, 46A and 46B.

FIG. 48A shows a topside view similar to FIG. 42, adding aone-dimensional angle-spreading lenticular filmstrip to input edge ofthe system's light guiding plate to widen the outgoing beam's horizontalangular extent, using a prism sheet rather than a plane mirror atoptapered light guiding plate.

FIG. 48B shows the configuration of FIG. 48A in perspective view.

FIG. 48C is another perspective view of FIG. 39A, showing theillumination system's underside output aperture.

FIG. 49 is a perspective view of the tapered-version of the lightguiding input engine 120, showing f angular extent of the light at thestart of the light guiding pipe, plus a graphic simulation sequence ofoutput light at various points along the pipe's output edge.

FIGS. 50A-50B, 50D, 50F and 50G all show perspective views of the slimprofile illumination system differentiated by the various lenticularfilm section configurations that have been simulated.

FIG. 50C shows a magnified view of the perspective of FIG. 50A.

FIGS. 50E and 50H show perspective views of two different near fielduniformity improvements.

FIG. 51A shows a side view of a schematic light extraction filmcross-section that underlies the concept behind a variable prism spacingdesign method, using conveniently enlarged prism coarseness.

FIG. 51B shows a perspective view of the design concept illustrated inFIG. 51A.

FIG. 51C shows a perspective view of a thin illumination system 1 withsuccessfully homogenized near field using the variable prism-spacingmethod.

FIG. 52 shows a graphical comparison of near field spatialnon-uniformity of one thin profile illumination system partiallysuccessful angular input edge correction as in FIG. 41H and one with thecomplete correction illustrated in FIG. 42C via the variable-prismspacing-method.

FIGS. 53A-53E show examples of cross-sectional schematic illustrationsof various stages in a method of manufacturing an illumination deviceincluding a transparent structure.

FIG. 54 shows an example of a flow diagram illustrating a method ofmanufacturing an illumination device.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

The following detailed description is directed to certainimplementations for the purposes of describing the innovative aspects.However, the teachings herein can be applied in a multitude of differentways. It is contemplated that the described implementations may beincluded in or associated with lighting used for a wide variety ofapplications such as, but not limited to: commercial, industrial, andresidential lighting. Implementations may include but are not limited tolighting in homes, offices, manufacturing facilities, retail locations,hospitals and clinics, convention centers, cultural institutions,libraries, schools, government buildings, warehouses, militaryinstallations, research facilities, gymnasiums, sports arenas, orlighting in other types environments or applications. In variousimplementations the lighting may be overhead lighting and may projectdownward a spotlight having an area that is larger (for example, severaltimes or many times larger) than an area of a light emitting surface ofa lighting device. Thus, the teachings are not intended to be limited tothe implementations depicted solely in the Figures, but instead havewide applicability as will be readily apparent to one having ordinaryskill in the art.

Implementations disclosed herein include a new class of thin plate-likeillumination systems (also, luminaries, illumination devices, lightingdevices, and lighting fixtures) whose square, rectangular, circular, orotherwise shaped illuminating beams are distributed uniformly overenlarged output apertures of reduced brightness, while remaining sharplydefined and well-directed in their illuminating extent from +/−5- to+/−60 degrees in each meridian, including all asymmetric combinations inbetween. Such light engines satisfy a wider range of general lightingservices than any of the known alternatives, including wide arealighting, spot lighting, flood lighting, task lighting, and wallwashing. In some implementations, a lighting device or illuminationdevice can include a light guide or light guiding plate, a light sourceconfigured to emit light into the light guide, and an optical couplerdisposed in an optical path between the light source and the lightguide. Some implementations can include an optical conditioner disposedbelow an illumination surface of the light guide, for example, a lightturning film or lenticular film. In some implementations, the lightengine can be sized and/or shaped to fit within the recess of a standardlighting fixture, for example, a recess for a parabolic aluminizedreflector (“PAR”) fixture. In other implementations, the light enginecan be differently sized and/or shaped than a standard lighting fixturerecess such that the light guide does not fit within the recess or suchthat the light guide fits in the recess with clearance on one or moresides.

Some implementations disclosed herein can include semiconductor lightemitting diodes (or LEDs) because of their intrinsic compactness,because of their rapidly improving light generating capacity, andbecause of their increasingly low cost commercial availability. Overtime, other suitable luminaire types may emerge based on organic LEDs(referred to as OLED), thin flat fluorescent sources, and flat microplasma discharge sources, to mention a few.

While LEDs can generally satisfy the need for thinness, applying LEDlight sources in accordance with the implementations disclosed hereininvolves a degree of adaptation for best mode usage. Suchimplementations can include light distributing engines includingcommercial LED emitters with appropriate heat extraction means,associated optical couplers, associated light distributing optics, andoptional light spreading elements. Further, the implementationsdisclosed herein can incorporate low voltage DC power controlelectronics needed to achieve sources of far-field illumination whosecross-sectional thickness is less than about 1-inch. Moreover, the newlight distributing engine configurations safely dilute the LED'sdangerously high brightness levels, without losing any of its otherfavorable lighting characteristics, such as tightly controlled beams ofillumination and well-defined illumination patterns.

Implementations disclosed herein enable luminaries notably more compactin their physical size (for example, approximately 2.5″×2.5″) andespecially thin in their cross-section (for example, approximately 5-10mm). Though small in size, lumen outputs provided by theseimplementations range from hundreds of lumens per luminaire tothousands. And the resulting output illumination is constrained to beamsorganized as tightly as +/−5 degrees, as broadly as +/−60 degrees, or asany asymmetric combination in between—each with a sharp enough angularcutoff to reduce off-angle glare (i.e., veiling glare) along with thespatially-even square, rectangular and circular far-field illuminationpatterns sought by lighting architects and users alike.

Some examples of practical applications incorporating the present thinillumination systems and other disclosed implementations have beenrepresented in U.S. Provisional Patent Application Ser. No. 61/104,606,entitled “Distributed Illumination System.” Extended practicalapplications of the implementations disclosed in this reference involvemore detailed system examples of the ease with which these thinillumination systems (also called luminaries and light distributingsystems) may be incorporated within the physical body thickness ofcommon building materials (as are used in forming commercial ceilingsand walls), electrically interconnected, and electronically controlled(individually and as an interconnected distribution).

An optical system 1 constructed in accordance with one form of athin-profile illumination system is indicated generally in the schematicperspective view shown in FIG. 1A and in the exploded perspective shownin FIG. 1B. This form can collect the light from a wide angle planeemitter (for example, an LED), uses a thin light guiding bar to providea strong degree of collimation in one meridian (for example, in adirection parallel to the illustrated x-axis), and then furtherprocesses this light with an equally thin light guiding plate thatretains the strong degree of pre-collimation in the first meridian whileadding an equally strong degree of collimation to the light in a secondmeridian orthogonal to the first (for example, in a direction parallelto the illustrated y-axis), so as to produce a uniform source of doublycollimated far field output light from a significantly enlarged outputaperture. The light distributing engine 1 can include at least twosubcomponents. For example, in some implementations, the lightdistributing engine 1 can include a light emitter 2 (such as anLED-based light emitter or LED light emitter) whose output light 4 canbe arranged to be redirected through output edge 8 into thecorresponding edge of an adjacent light distributing optic 9 whoseinternal design can be arranged to transform incoming output light 4into well-organized output light 10 that is evenly distributed over thelight distributing optic's significantly enlarged output aperture 11 ina multiplicity of overlapping beams across that aperture whose lightcones are limited in angle to +/−θ₁, and +/−θ₂ in the light distributingengine's two orthogonal output meridians (e.g., the ZX meridian and theZY meridian). Light emitter 2, in this form, can include anedge-emitting light bar, an edge-emitting light pipe, an edge-emittinglight guide, or a light spreading pipe 18 having a single LED emitter 3at its input, and an internal design arranged so that the edge-emittinglight pipe's output light 4 is distributed evenly along the length ofits output edge 8, and pre-collimated more narrowly in one meridian (forexample, ZY meridian inclusive of the plane common to Y-axis 5 andZ-axis 6) than in the other (for example, ZX meridian inclusive of theplane common to X-axis 6 and Z-axis 6). Light distributing optic 9, inthis form, can receive output light 4 from light emitter 2 along outputedge 8, and can comprise a transparent (for example, a dielectricmaterial) light guiding plate or light guide 28 and associated lightextracting and redirecting elements 34, whose internal design enablesoutput light 10 to be directed outwards (downwards as shown) from justone of its plane aperture surfaces 11, collimated in both outputmeridians (ZX and ZY as above).

Orientation of parts, light directions and angular extents are relatedto the three orthogonal crystallographic axes 5, 6 and 7, or Y, Z and Xrespectively.

As one example, LED light emitter 2, consists of a single LED emitter 3that may contain one or more LED chips within its output aperture (notillustrated), a coupling optic 14 that may be a rectangularetendue-preserving angle-transforming reflector (RAT) designed tocollect and transport light efficiently from emitter 3 to input face 16of transparent dielectric light guiding bar 18 with a pre-selectedangular distribution in each orthogonal meridian, separated from lightdistributing optic 9 by a thin air-gap 20. Transparent light guiding bar18 itself can include two co joined optical elements 22 and 24,transparent light guiding bar (pipe or guide) 22 having square (orrectangular) cross-section with smoothly polished sides (or edges) thattransmits input light flowing within by total internal reflection, andlight extracting film 24 placed adjacent to one edge of light guidingbar 22, whose detailed design and composition is explained in moredetail further below, extracts a fraction of the light flowing withinbar 22 striking it everywhere along its length, and thereby collimatesthat light in one meridian (Y, 5) without changing the angulardistribution of the extracted light in the other meridian (Z, 6), whileredirecting all extracted light over the bar's length substantially inan outwards direction through output edge 8 along the system's X axis 7.

Light distributing optic 9 can include two co joined optical elements,one being transparent light guiding plate 28, and the other beingadjacent light extracting film 34. Light guiding plate 28 has a flat andpolished input edge 25, and two flat and polished plane faces, 11 and32. In some implementations, the light guiding plate 28 can include adielectric material. Light extracting film 32, in the example of FIGS.1A-1B is laminated to plane face 32 (in an analogous form, it may beplaced just beyond plane face 11). Design and composition of lightextracting film 32 (described further below) enables a fraction of thelight striking everywhere along its length and over its area to be freedfrom total internal reflections within plate 28, collimated in onemeridian (X, 7) without change to the pre-collimated angulardistribution of light in the other (Y, 5), and redirected as adoubly-collimated output beam 10 heading outwards along the element'soutput axis (Z, 6) or some other output light direction at an angle toit.

The following meridian planes will be discuss with reference to theexamples that follow. The horizontal meridian (for convenience alsocalled the XY meridian) is taken as the XY plane parallel to the largeface planes of light distributing optic 9. The first vertical meridian(for convenience also called the ZY meridian) is orthogonal to thehorizontal meridian, and taken herein as the ZY plane parallel to inputedge 25 of light distributing optic 9. The second vertical meridian (forconvenience also called the ZX meridian) is orthogonal to both thehorizontal meridian and the first vertical meridian, taken herein as theZX plane. The Cartesian system of reference throughout comprises Y-axis5, Z-axis 6 and X-axis 7.

FIG. 1C is a partially exploded perspective view that illustrates moreclearly the system's various light-flows and the corresponding angulardistributions created by the doubly collimating actions. In general,input light from LED emitter 3 can be collected by, and passes through,the input and output apertures of coupling optic 14, wherein the inputlight is transformed to beam 36 having an optimized angular distributionfor coupling into input face 16 of light guiding bar 18 along Y-axis 5.As beam 37 passes through the length of bar 18, it can be arranged toturn 90 degrees from Y-axis 5 to X-axis 7 by the action of lightextracting film 24, and is output everywhere along edge face 8 asedge-emitted light beam 38, collimated strongly in the horizontal XYmeridian to angular width +/−θ_(Y) (in air) 40 and more weakly asangular width 42 in the vertical ZX meridian. Light beam 38 then couplesthrough edge face 25 into the body of light distributing optic 9 and itslight guiding plate 28 as beam 39 directed along X-axis 7. As beam 39passes through the length and volume of light guiding plate 28, it turns90 degrees everywhere from its initial propagating X-axis direction 7 toit output Z-axis direction 6 as beam 45 by the action of lightextracting film 34. Beam 45 is collimated strongly in the vertical ZXmeridian narrowing to angular width +/−θ_(X) (in air) 41 by its passagethrough light distributing optic 9, but retains its equally strongpre-collimation +/−θ_(X) in plate 28 (+/−θ_(Y) in air) in the horizontalZX meridian as angular width 44. The result is well-collimated far fieldoutput illumination 10 emanating into air from the surface area of planeface 11 of light distributing optic 9, illumination 10 beingequivalently well-collimated in both output meridians, +/−θ_(Y) in thevertical ZY meridian (pyramidal face 46) and +/−θ_(X) in the vertical ZXmeridian (pyramidal face 48).

Wide angle light beam 36 can be output from coupling optic 14, in thisexample a rectangular etendue-preserving angle-transforming (RAT)reflector with an etendue-preserving angular distribution in each of itstwo orthogonal output meridians (XY and ZY), that can be chosen based atleast in part on the efficiency of input coupling to input face 16 oftransparent light guiding bar 18 and the spatial uniformity of outputbrightness produced along the length of the bar's output edge (or face)8. The light guiding bar's resulting far-field output beam 38 (shownsymbolically as a pyramidal solid) is well collimated in the horizontalXY meridian, and as such achieves a reduced angular width 40 (alsoreferred to as a reduced angular extent), designated as +/−θ_(Y) (2θ_(Y) full angle). Angular distribution of output light 38 in theorthogonal ZX meridian is substantially unchanged by its passage throughlight guiding bar 18 and retains the original wide angle input beam 36characteristic of coupling optic 14 in its vertical ZY meridian, in thiscase a RAT reflector. Angular cone 42 in this vertical ZX meridian isarranged to achieve the most efficient optical coupling of light passingfrom output edge 8 and into input edge 25 of corresponding light guidingplate 9. Input angle 42 is also chosen to achieve the highest spatialuniformity of the output light extracted across the component's fulloutput aperture surface 11, as will be explained in more detail furtherbelow. As input light cone 38 enters through the input edge 25 of lightdistributing optic 9, it undergoes total internal reflection withinplate or light guide 28. The angular width of light flowing in theplate's horizontal XY plane is represented symbolically by internal beamcross-section 43, and retains the angular extent 40 of the incominglight in this meridian. The angular relationship between this horizontallight in the air surrounding light distributing optic 9 and thecorresponding light within in the medium of plate 28 is simplySin(θ_(Y))=n Sin(θ_(YY)) with n being the refractive index oftransparent light guiding plate 28.

Etendue-preserving RAT reflector 14 has an input aperture dimensioned d₁by d₂ (not illustrated) designed to match the output aperture of LEDemitter 3 (not illustrated), also dimensioned substantially d₁ by d₂.RAT reflector 14 has an output aperture that is D₁ by D₂. RAT reflector14 is four sided and with each reflector sidewalls mathematically-shapedto preserves etendue between input and output apertures, so transformingthe LED's wide angle output emission to etendue-preserving output lightthat then passes through the RAT reflector's output aperture in bothmeridians of the light guiding pipe (or bar) 22 with an angular extentsubstantially equaling +/−θ, by +/−θ₂, where +/−θ₁ and +/−θ₂ can bedetermined by the applicable etendue preserving Sine Law,θ₁=Sin⁻¹(d₁/D₁), where d₁ and D₁ refer to the input and output aperturedimensions in each meridian, d₁ and d₂ (in spatial dimensions), D₁ andD₂ (in spatial dimensions) and θ₁ and θ₂ (in angular dimensions).

As will be established further below, the RAT reflector's output anglesfor light coupling to the input aperture of the light guiding pipe canbe reduced to about 50-55 degrees in each half-angle in air, i.e., +/−θ₁and +/−θ₂. The design values for d₁, d₂, D₁ and D₂ can be adjustedaccordingly, depending on the dimensions of the LED emitter 3 beingused. The length or physical separation between input and outputapertures of RAT reflector 14, L, is substantially as prescribed by theSine Law, L=0.5 (d_(i)+D_(i))/Tan θ_(i) with L being the larger of thelengths calculated in each of the RAT reflector's two meridians, but maybe foreshortened by 10% to 40% without significant penalty in couplingperformance.

Doubly collimated (or cross collimated) output light is distributedsubstantially uniformly over the surface area of its output aperture 11by the light-distributing engine of system 1. The doubly collimatedfar-field beam 10 is further represented in FIG. 1C bycomputer-simulated profile 50 explained further below. When θ_(Y)=θ_(X),as in the present example, output beam 10 has a square cross-section.When θ_(Y)>θ_(X) or when θ_(Y)<θ_(X), which is also possible, outputbeam 10 has a rectangular cross-section.

This particular form of the present disclosure can be distinguished notonly by the cross-sectional thinness achieved with the combination oflight emitter 2 and light distributing optic 9, but also by virtue ofthe doubly-collimated output beam that results from their collectiveoptical behaviors, one degree of output beam collimation coming fromedge-emitting light emitter 2 and the orthogonal degree of output beamcollimation coming from the light guiding, extracting and redirectingnature of light distributing optic 9. While some prior art examples ofthin illumination systems have produced collimated light in one outputmeridian and not in the other, the present disclosure producesindependently collimated light in both orthogonal output meridians.

Doubly-collimated output beam 50 may be expanded externally to createany orthogonal set of output beam angles larger than +/−θ_(Y) by+/−θ_(Y′) as shown in the perspective view of FIG. 1D by adding one ortwo angle-spreading film sheets 52 and 53 just beyond output aperturesurface 11 of system 1. Such films can be relatively thin (for example,less than 0.250 mm), and thus add little additional thickness to thelight distributing engine's slim cross-section.

A special lenticular class of angle-spreading film sheets will beintroduced and described further below as an additional feature of atleast some implementations of this disclosure. Such film sheets areapplied to change (i.e., widen) the angular spread of light passingthrough them in only one meridian and not in the other. Orienting twosuch lenticular sheets with their lens axes oriented substantiallyorthogonal to each other, as in FIG. 1D, enables a complete family ofwider far field beam patterns to be achieved, with a different angularwidth, 56 and 58, affected in each meridian. The lenticular sheetsincluded within this disclosure can be distinguished by their ability topreserve the square and rectangular far field beam shapes (orillumination patterns) characteristic of these particular thin-profiledoubly collimating light distributing engines of illumination systems 1.If the far field output beam from system 1 in FIGS. 1A-1C is +/−5degrees by +/−5 degrees and makes a substantially square far-fieldillumination pattern, just as one example, some possible far field beamalternatives 56 and 58 for the system of FIG. 1D are +/−10 degrees by+/−10 degrees, +/−5 degrees by +/−20 degrees, +/−30 degrees by +/−30degrees, and +/−25 degrees by +/−15 degrees, to mention but a few. Whenthe expanded angular ranges are the same in each meridian, the resultingillumination pattern is substantially square. When the expanded angularranges are different in each meridian, the resulting illuminationpattern is substantially rectangular.

Output beam angle spreading may also be achieved using more-conventionaldiffusing materials as have been described in prior art, such asspherical lenticular lens sheets and highly asymmetric light shapingdiffusers based on holographic (diffractive) principles. In neithercase, however, are the characteristic advantages of sharp angular cutoffmaintained nor are square or rectangular beam patterns achieved. The farfield output beam patterns obtained using conventional prior artdiffusers in the manner illustrated in FIG. 1D can be either circular orelliptical in nature. Additionally, similar output beams may be achievedusing diffusers.

An optical system 1 constructed in accordance with anotherimplementation of this thin-profile illumination system is showngenerally in the perspective views of FIGS. 2A-2E. One exampledifference between this implementation and the implementationillustrated generally in FIGS. 1A-1D is that in this form the LED lightemitter 2 provides strongly pre-collimated input light in one meridiandirectly from the output of coupling optic 14 to the input edge of lightdistributing optic 9, doing so without need of light guiding bar 18 asthe pre-collimating intermediate. In this implementation, coupling optic14 can be rectangular etendue-preserving angle-transforming reflector(RAT), whose collimating power is applied to narrow the LED emitter'sangular extent in the horizontal XY meridian to +/−θ_(Y) (in air)becoming +/−θ_(YY) in light distributing optic 9 upon coupling (as inangular extent 44 of coupled beam representation 43 as shown in FIG.2A). The RAT reflector's cross-meridian ZX is used as above to providejust enough collimation to optimize light coupling performance(efficiency and uniformity) with regard to light distributing optic 9.In this implementation, the width 60 of light distributing optic 9(designated as W) approximately equals the XY meridian output aperturewidth 61 of RAT reflector 14 (designated D₁), with D1 established by theclassical Sine Law as approximately d₁/Sin θ₁, with d₁ being horizontalwidth 63 of output aperture frame 62 of LED emitter 3 (which asmentioned earlier is d₁ by d₂ horizontally and vertically).

While a more detailed example of this form is provided further below, aninitial example is provided here to give scale to the generalizedillustration of FIG. 2A. When d₁=3.6 mm, which is one possibility, andwhen the XY meridian's pre-collimation is to be +/−θ₁=+/−θ_(y)=10.5degrees, which is another possibility, D₁=19.75 mm, and the RATreflector's ideal length 64 (designated as L) is also by the Sine Law,0.5(d₁+D_(i))/Tan θ₁=63 mm, which as mentioned above, can beforeshortened by 10%-40% without serious penalty.

Cross-sectional thickness 66 of the light distributing engine 1 in FIG.2A (designated as T) is approximately equal to the RAT reflector'svertical output aperture dimension 67 (designated as D₂), which in turnis driven by vertical dimension 65 (designated as d₂) of the LED emitteroutput aperture frame 62. When d₂ is for example 2.4 mm, which isanother reasonable possibility, and when the desired collimating angleis +/−55 degrees, as explained further below, D₂, by the Sine Law,becomes d₂/Sin θ₂=2.9 mm, which emphasizes the potential thinness oflight distributing engines according to the implementations provided inthis disclosure.

FIG. 2A is a partially exploded perspective view illustrating thegeneral constituents of this form of doubly collimating lightdistributing engine 1, which are LED emitter 3, coupling optic 14, lightdistributing optic 9, and doubly collimated output illumination 10,generally directed along (or at an angle to) Z-axis 6. Substantially allemitted light from LED emitter 3 is collected by the correspondinglysized input aperture of coupling-optic 14 which can be a rectangularetendue preserving angle transforming (RAT) reflector. Thensubstantially all collected light (less reflection and absorption losswithin the RAT reflector's 4-sided reflecting structure 68) is coupledfrom the reflector's rectangular D₁ by D₂ output aperture to thecorrespondingly sized rectangular input aperture of light distributingoptic 9. The in-coupled light is represented symbolically, as above, bypropagating beam 43, which has pre-collimated angular extent +/−θ_(YY)as shown within the horizontal XY meridian light distributing optic 9,but satisfies the boundary conditions of total internal reflection ateach of the light distributing optic's four external surface boundaries.Then, as explained generally above, doubly collimated outputillumination 10 emanates uniformly over the surface area of outputaperture plane 11 as a result of pre-collimation in the horizontal XYmeridian and interactions between propagating light 43 and lightextracting film 34 in the vertical ZX meridian. In this implementation,+/−θ_(X) collimation 69 in the ZX meridian (pyramidal beam surface 70)is the result of actions within light distributing optic 9, and +/−θ_(Y)collimation 71 in the vertical ZY meridian (pyramidal beam surface 72)is the result of the RAT reflector's pre-collimation +/−θ_(Y) (in air)initially in the horizontal ZY meridian.

FIG. 2B is a perspective view similar to FIG. 2A but illustrating themulti-segment capacity of this form of this disclosure, in this casewith four otherwise identical light distributing engines 1 of the formillustrated in FIG. 2A. The ability to assemble a contiguous, orsubstantially contiguous, array of parallel engine segments extends therange of output lumens significantly. About three light distributingengines of the geometrical dimensions illustrated in FIG. 2A can be usedto replace each light distributing engine of the square aperture formshown in FIGS. 1A-1D, in some implementations.

FIG. 2C is a perspective view illustrating the combination of seven (7)separate light distributing engine segments in the form shown in FIG.2A.

The multi-segment doubly-collimating engine variation illustrated inFIG. 2C shows no discrete, demarcation lines between the seven separateengine segments, either between the individual coupler elements (forexample, individual etendue-preserving RAT reflectors) or between theseven corresponding light distributing optic segments into which eachRAT reflector's output light is coupled. While each coupling optic 14 isas discretely separated from each other as the examples in FIGS. 2A-2B,the same degree of physical separation is not required for satisfactoryperformance of the corresponding light distributing optic 9. The generalqualities of the resulting doubly-collimated output illumination 10 aresubstantially equivalent whether seven individual light distributingoptic segments are used, as in FIG. 2B, or whether a single segment madeto be the same size as covered by seven individual segments were usedinstead, as in FIG. 2C. The illumination system's far field output beam10 exhibits essentially identical angular widths +/−θ_(X) in meridian ZX(e.g. pyramidal surface 70) and +/−θ_(Y) in meridian ZY (e.g., pyramidalsurface 71).

Whether the resulting multi-segment light distributing engine 1incorporates an LED light emitter array of physically discrete segmentsas illustrated in FIG. 2B, or is fabricated as a single body made withindividual light transmission channels 68, as imagined in the example ofFIG. 2C, depends on manufacturing and packaging preferences.

FIG. 2D is a partially exploded perspective showing the seven-segmentLED light emitter array of FIG. 2C by itself at greater magnification.Element 74 is the first of 7 sequential coupling optic segments.Pyramidal solid 76 is a symbolic representation of the intermediatelypre-collimated output light generated by the collective output ofseven-segment LED light emitter 2, indicating its angular extent 78 inthe vertical ZX meridian as +/−φ_(Z), and its more strongly-collimatedangular extent 80 in the horizontal XY meridian as +/−θ_(Y). As in theexamples above, a single beam representation is used for convenience,representing a continuum of illumination from the rectangular outputapertures of all seven RAT reflectors. The illustration (FIG. 2D) alsoshows an exploded (and magnified) view of illustrative LED emitter 3,which in this example has a square aperture bounding ring 82 thatsurrounds the emitter's 4 separate chips 84, arranged internally in a2×2 array, and electronic substrate 86 (containing means for electricalinterconnections 88 and heat extraction).

The angle-spreading film sheets 52 and 54 introduced in FIG. 1D may beapplied to both the single segment and multi-segment forms of the lightdistributing engines of FIGS. 2A-2D, as will be shown in FIG. 2E.

FIG. 2E is a perspective view of FIG. 2D exploded to reveal theindividual sections of input engine 60, while adding twoorthogonally-aligned angle-spreading sheets 52 and 54 (as in FIG. 1D).Such sheets are applied externally as illustrated just below lightdistributing optic 9 so as to modify (i.e., widen) the angular extents90 and 92 of the system's resulting far field output beam in one or bothmeridians. The unmodified narrower angular extents 70 and 72 are showndotted as a reference.

Practical operating applications of the thin doubly collimating lightdistributing engines 1, whether arranged in the square aperture form ofFIGS. 1A-1D or the multi-segment form of FIGS. 2A-2E, require structuralchassis plates to hold and align the individual constituents, includingas well the associated power controlling electronic circuitsinterconnected with both an external supply of DC voltage and with thepositive and negative electrical interconnections 88 provided on eachLED emitter 3 (as in FIG. 2D). Moreover, heat sink fins and heatspreading elements can be incorporated to dissipate heat from the LEDemitter 3. While such system level light distributing engine detailshave been introduced separately in U.S. Provisional Patent ApplicationSer. No. 61/104,606, representative illustrations for each case will beprovided further below.

Before doing so, the underlying details are described for someimplementations of this disclosure, with FIGS. 3-21, 26-28, and 31-43optionally associated with the doubly-collimating square aperture lightdistributing engine introduced generally by FIGS. 1A-1D, and with FIGS.30A-30B optionally associated with the doubly collimating multi-segmentlight distributing engine introduced generally in FIGS. 2A-2E.

FIG. 3A shows a perspective view of an example of an implementation ofthe present light distributing engine in its single-emitter squareoutput aperture form, generally shown in FIGS. 1A-1D. LED light emitter2 in this example includes an LED emitter 3 and an etendue-preservingRAT reflector form of coupling optic 14 as shown in FIGS. 1A-1D, but thegeneralized edge-emitting light guiding bar (or pipe) 18 can be formedby a tapered light guiding pipe 100 and a separately facetted(micro-structured) light extraction film 102 that is optically coupledin this example to the tapered backside edge of pipe 100 by transparentcoupling layer 106. The output edge of tapered light guiding pipe 100emits pre-collimated output light across air gap 20 into the input edgeof light distributing optic 9, which can be a tapered light guidingplate 112 having a separately facetted (micro-structured) lightextraction film 114 (substantially the same micro-structure as lightextraction film 102) and optically coupled in this example to thetapered backside edge of plate 112 by transparent coupling layer 118(substantially the same as transparent coupling layer 106).

FIG. 3B is an exploded version of the elements shown in the perspectiveview of FIG. 3A that reveals previously hidden structural details.

FIG. 3C provides a magnified exploded view of the geometricalrelationships between LED emitter 3 (as illustrated in FIG. 2D),etendue-preserving RAT reflector 14 (in this example illustrated as ahollow 4-sided reflecting bin having symmetrically shaped reflectingsidewalls 131) and the corresponding input portion of tapered lightguiding pipe 100, including its square (or rectangular) input face 128(sized generally to match the D₁ by D₂ output aperture dimensions (133,135) of RAT reflector 14 as explained above).

FIG. 3D is a perspective view illustrating the relationship between thelight-cone 36 (as in FIG. 1C) output from illustrative RAT reflector 14,and the reduced-angle optical coupling to the dielectric medium of lightguiding pipe 100, shown as (dotted) cone 140. In some implementations,light guiding pipe 100 can be made of low optical loss sources of eitherpoly methyl methacrylate (for example, PMMA or acrylic) orpolycarbonate. Generally, lowest loss is possible when using opticalgrade PMMA. When light guiding pipe 100 has a 3 mm×3 mm squarecross-section, and is made, for example, of polycarbonate, refractiveindex 1.59, coupling performance can be achieved, for example, whendotted light cone 140 is approximately in the range of +/−30 degrees inboth meridians (X and Z). This requires the angular extent of light cone36 in air to be +/−Sin⁻¹ [1.59 Sin(30)] or +/−52.6 degrees in eachmeridian. Coupling performance can be achieved with a slightly widerangular range when using PMMA and its lower (1.49) refractive index, insome implementations.

FIG. 3E is a side view of the input elements isolated in FIG. 3D,showing the detailed angular distributions of the light as its conveyedfrom LED emitter 3, through illustratively hollow etendue-preserving RATreflector 14, and across a small air gap (exaggerated in scale forvisual convenience) into the initial region of light guiding pipe 100.Radiation pattern 142 corresponds to the light output from the outersurface of the LED chips of LED emitter 3, and from its nearly circularcross-section, indicating an almost perfect +/−90-degree Lambertianlight distribution. As this wide angular distribution passes throughillustrative RAT reflector 14 it is concentrated slightly in angularextent to one having in this example, +/−52.6-degree extent 144 in airby its etendue-preserving passage through RAT reflector 14. Then, oncecoupled into light guiding pipe 100, this light distribution compressesby Snell's Law to one having about a +/−30-degree extent 146 within thedielectric medium (taken as polycarbonate just for this example).

FIG. 4 is a top view of the complete doubly-collimating square aperturelight distributing engine system 1, as depicted in the perspective viewsof FIG. 3A-3B, showing the associated symmetry-driven geometricalrelationships in existence between the LED light emitter 2, a taperedlight guiding pipe (or bar) 100 attached to facetted light extractionfilm 102 and the light distributing optic 9, which can be a taperedlight guiding plate 112 attached to facetted light extraction film 114.Equation 1 relates the prevailing geometrical relationships betweentapered light guiding pipe 100 thickness 150 (along X-axis 7) expressedas THKB, tapered light guiding pipe 100 length 152 (along Y-axis 5)expressed as LB, tapered light guiding plate 114 length 154 (alongX-axis 7) expressed as LP, the taper angle 156 of tapered light guidingpipe 100 expressed as α_(b), the corresponding taper angle 157 (notshown in FIG. 4) expressed as α_(p), the knife edge thickness 158 oftapered light guiding pipe 100, and the corresponding knife edgethickness 159 (along Z-axis 6) expressed as KP (not shown in FIG. 4). Inthe present example for simplicity, α_(p)=α_(b) and THKB=THKP.THKP=TKHB=(LP)Tan α_(p) +KP  (1)

FIG. 4 also shows a top view of the highly collimated edge-emitted lightdistribution 162 produced (generally directed along X-axis 7) and spreadover most of the output edge 126 (see FIG. 3B) of tapered light guidingpipe 100 within LED light emitter 2 as the light couples efficientlyacross air gap 20 into the body of tapered light guiding plate 112.Light distribution 162 is thereby representative of a continuum ofsubstantially equivalent light distributions 162 running parallel toeach other along edge plane 126 passing through points 159 and 161.

One example optical element utilized in this implementation ofthin-profile light distributing engine 1 is the tapered light guide,whether deployed in its rod, bar, pipe or steeple-like form within LEDlight emitter 2 as tapered light guiding pipe 100, or in its largerrectangular area tapered plate form as light guiding plate 112 as partof light distributing optic 9. The ability to collimate light in onemeridian (and not the other) stems from the light spreading broughtabout by total internal reflections of light inside the tapered lightguides (whether 100 or 112) combined with interactions between theguided light and the facetted light extraction films (102 or 114)attached to (or placed in optical proximity with) one of the taperedlight guide faces (as shown in FIG. 3B). But the ability to collimatelight in both meridians (e.g., producing the narrowly defined square andrectangular far-field output beam profiles shown in FIGS. 1C, 1D, 2A,2C, and 2E), stem from the sequential use of two tapered lightguide-extraction film combinations, one for each orthogonal meridian.Substantially un-collimated light from LED emitter 3 is firstpre-collimated in one meridian by the first tapered light guide system(guide 100 plus film 102). This processed light is received by thesecond tapered light guide system (guide 112 plus film 114), whichcollimates the light in the substantially un-collimated meridian, whiletransmitting light in the pre-collimated meridian without change. Thistwo-step processing results in output light that is collimated in bothorthogonal output meridians.

In other words, the LED light emitter 2 within this form of lightdistributing engine collimates in one output meridian only, while thelight distributing optic 9 collimates in the other output meridian only,while simultaneously turning (or redirecting) the doubly-collimatedoutput light direction at some desired angle to the output aperture'ssurface normal.

The two communicating subsystems, LED light emitter 2 and lightdistributing optic 9 are separated from each other by a small air-gap20, with output edge 126 of one well-aligned with input edge 121 of theother.

Explicit examples are provided in FIGS. 5-20 below to explain (andprovide means for optimizing) the underlying physical mechanismsresponsible for the double collimation (and angular redirection)critical to this form of the present light distributing engine.

As described above, the light emission from single LED emitter 3 (whichmay contain one or more individual LED chips) couples emitted light toinput face 128 of tapered (dielectric) light guiding pipe (bar or rod)100 by means of a coupling optic 14, that can be a square or rectangular(etendue-preserving) angle-transforming (RAT) reflector, whose fourspecularly reflecting sidewalls are mathematically shaped at every pointto reflect light at an angle to preserve etendue from the LED emitter'ssquare or rectangular output aperture (as in 82 of FIG. 2B) to thesquare or rectangular input face 128 of tapered light guiding pipe 100(according to the Sine Law cited above), while converting the LEDemitter's near Lambertian input angles to an angular range more suitedto efficient light coupling to tapered light guiding pipe 100.

Tapered light guiding pipe 100 is made using a suitable molding processsuch as casting, injection, or compression-injection whose toolingenables formation of the flat plane mirror-quality edge surfacesillustrated, for example, using a transparent optical quality dielectricmaterial having an optical absorption coefficient in the visiblewavelength band that is as low as possible. Two suitable choices arepolycarbonate, refractive index 1.59 and polymethyl methacrylate (alsoreferred to as PMMA or acrylic), refractive index 1.49. Of these twolight guiding materials, PMMA can be for its lower level of opticalloss. Arbitrarily, polycarbonate is used in the following examples.

More details on the pipe's tapered geometry are provided further below,but for the present example, the pipe's input face 128 is 3 mm×3 mm,it's effective taper length 154 (designated as α_(b) in FIG. 4) is 57mm, so that by geometry, its associated taper angle 156 (designated asα_(b) in FIG. 4), is α=Tan⁻¹(3/57)=3 degrees, independent of therefractive index of the material used. With an illustrative 3-degreetaper angle and 3 mm by 3 mm input face cross-section, light guidingpipe 100 draws down to knife-edge or peripheral edge 158, which can belimited to a 50 μm thickness or less, to maximize the effective outputefficiency of LED light emitter 2. Light guiding pipe 100, asillustrated in these examples, begins with a linear extension 150 notcounted in its illustrative 57 mm effective taper length, as seen mostclearly in FIG. 4.

The tapered light guiding plate 112 can be sized to match (orsubstantially match) the rectangular geometry of the tapered portion oftapered light-guiding pipe 100. That is, edge face 126 of light guidingpipe 100 and corresponding edge face 121 of light guiding plate 112 canhave substantially the same rectangular length and thickness so as tomaximize their optical overlap and coupling efficiency. These conditionsare generally satisfied when tapered light guiding plate 112 has across-sectional thickness matching the corresponding thickness oftapered light guiding pipe 100 (for example, in this case 3 mm), andwhen tapered light guiding plate is sized to match the effective length154 (designated LB in FIG. 4), making it in this case 57 mm by 57 mm.The taper planes (101 and 122) in both the tapered light guiding pipe(taper plane 101) and tapered light guiding plate (taper plane 122) ofthe examples contained herein are oriented so their outside surfaces areeach facing in the opposite direction of the intended direction ofoutput light. The reverse orientations are also acceptable.

The two light extraction films (102 and 114) can be formed using anoptical material having the same or higher refractive index as thetapered light guiding pipe (or plate) they are being combined with. Thefacetted microstructures of the two light extraction films may beidentical, or made to be different (as will be illustrated in an examplediscussed below). In all ensuing examples, however, both lightextraction films (film 102 for pipe 100 and film 114 for plate 112) areillustrated as being laminated (i.e., optically coupled) to theirassociated taper plane (plane 101 for extraction film 102 and plane 112for film 114) which can be accomplished using an optical coupling layer(layer 106 for extraction film 102 and layer 118 for extraction film114), the optical coupling layers having substantially lower refractiveindex than either surrounding extraction film, guiding pipe or guidingplate material.

One material combination for light guides and extraction films for bothlight extraction films (102 and 114) and both light guides (lightguiding pipe 100 and light guiding plate 112) can include polycarbonate,refractive index 1.59. For this combination each light extraction film(film 102 and film 114) can be laminated to its light guidingcounterpart using an optical coupling layer made of a PMMA orsilicone-based adhesive (i.e., layer 106 and layer 118) having arefractive index no greater than that of pure PMMA, 1.49 or lower. The0.1 refractive index difference between polycarbonate and pure PMMAfacilitates light extraction, as illustrated below. Adhesives Researchmanufactures a wide range of suitable commercially available opticalcoupling layer materials under their brand names ARclad™ and ARclear™.

Another material combination for light guides and extraction films forboth light extraction films (102 and 114) and both light guides (lightguiding pipe 100 and light guiding plate 112) can include PMMA,refractive index 1.49. For this combination, each light extraction film(film 102 and film 114) can be laminated to its light guidingcounterpart, for example, using an optical coupling layer made of alower refractive index PMMA-based or silicone-based adhesive (i.e.,layer 106 and layer 118). One example of a low-index PMMA opticalcoupling layer is 50-μm thick ARclear™ 8932 with refractive index 1.41.This choice of pressure sensitive laminating adhesive is alsomanufactured by Adhesives Research and designated as an optically clearsilicone transfer adhesive having low haze and high clarity. The 0.08refractive index difference between polycarbonate and standard PMMA, andbetween standard PMMA and the low-index form of PMMA, equallyfacilitates light extraction.

The tapered light guide (whether pipe 100 or plate 112) can be animportant building block because, along with the angular preconditioningof input light which can be from LED emitter 3 provided by theetendue-preserving RAT reflectors 14, the tapered light guide enablesuniform output luminance to be achieved along its edge length for thepipe and the length of its cross-sectional area for the plate, withapproximately equal division of light between its two plane boundarysurfaces.

Although the general properties of tapered light guides have alreadybeen described and have been utilized in a few early fluorescentlighting applications, prior art descriptions are insufficientlyprepared for present purposes. No prior art teaching has everanticipated the deliberate combination of a tapered light guiding pipewith a tapered light guiding plate in a conjunctively orthogonal mannerthat provides well-collimated output light from the system in both itsoutput meridians (see FIGS. 1A-1D, 3A-3B and 4). Prior art teaching hasnot anticipated the unique angular input requirements that arise whencombining two tapered light guides according to the constraints ofequation 1 (see FIG. 4). Prior art examples have not provided a suitablemeans for coupling wide emitting angle LEDs to tapered light guidingbars so as to output collimated light evenly and homogeneously along thebar's entire aperture length (see FIGS. 3C-3E and 5A-5C). And, prior artteaching has not anticipated the underlying relationships between inputcoupling conditions and the resulting near field spatial uniformity ofthe tapered light guide system that takes place in practicalimplementations, unique to such double-collimating illumination systems(see for example FIGS. 48A-48C, 49, 50A-50H, 51A-51C, and 52).

For these reasons, the underlying tapered light guide behaviorspertinent to this disclosure will be established and then some exampleimplementations will be discussed.

All results provided herein, including the typical angular distributionsshown in FIGS. 1C and 3E above as initial examples, represent thoseobtained from realistic non-sequential optical ray-trace simulationsmade using the optical system modeling software called ASAP™ 2006,version 2, release 1 and ASAP™ 2008 version 1, release 1, manufacturedby the Breault Research Organization, Tucson, Ariz., which has beenarranged to allow correctly for multiple splits of the implicit Fresnelreflections that occur at all light guiding boundaries, with thedielectric media surrounding these boundaries, taken as air, (n_(MED)=1)as a typical example.

The schematic cross-section of the tapered light guide that underliesthe simulated behavior of both light guiding pipe 100 (Z-Y plane) andlight guiding plate 112 (Z-X plane) is given in FIG. 5A. Illustrativevalues are taken from the example described above. The prevailing taperangle 166, α=α_(p)=α_(b), is 3 degrees, taper length 168, L=LB=LP, is 57mm, light guide thickness 170, THK=THKP=THKB, is 3.037 mm, knife-edgethickness 172, K=KB=KP, is 50 μm, and the dielectric light guidematerial (medium), illustratively polycarbonate, has a refractive indexof 1.59. Comparable examples could be based on PMMA. The angularcross-section of simulated input light 144 (as in FIG. 3E) is applieduniformly over input face 128. When taper angle 166, knife edgethickness 172 and guide length 168 are fixed, the expression for guidethickness 170 follows from equation 1, THK=L Tan α+K. So, for theillustrative values, THK is geometrically, 3.037 mm (approximately 3mm).

FIG. 5A also shows the simulated (computer generated) output beams 180(upward taper side) and 182 (downward plane side), and their respectiveangular inclinations γ_(T) (upward taper side) and γ_(P) (downward planeside) 190 and 192 that arise from total internal reflection failures oflight rays transmitting within tapered light guide (whether 100 or 112)along both tapered mirror plane 184 (top side) and its flat mirror plane186 (bottom side). Topside output beam 180 is found to incline at abouta 16.5-degree angle 190 to the axis parallel to the guide's plan flatboundary plane 186, whereas bottom side output beam 182 is found toincline at a 19.5-degree angle 192 (for the illustrative case ofpolycarbonate, n=1.59). The approximately 3-degree difference betweenthese two results is due primarily to the tapered light guide's 3-degreetaper angle α, 166. The angular width (or extent) of each beam, FWHM, isabout +/−6 degrees. Approximately 50% of input light 144, in lumens, isfound within each far field output beam depicted. Changing the guidingmedium to a slightly lower refractive material such as PMMA (n=1.49) canreduce each output beam angle only about 1-degree, an has little effecton each beam's angular extent.

FIG. 5B shows three examples of the near field spatial non-uniformities(194, 196 and 199) that can result on tilted topside taper surface 184as a consequence of the angular extent of input light that is coupledinto entrance face 128 of the light guide cross-section of FIG. 5A.Spatial light profiles (194 and 196) arise on tilted top side tapersurface 184 for two illustratively different input light conditionswithin guide 100 or 112, one example being input light that transmitsinitially with a +/−52.6-degree cone (in air) in the plane of thecross-section (profile 194) and another example being light thattransmits initially with a narrower +/−38.97-degree cone (in air) in theplane of the cross-section (profile 196). The corresponding spatialprofiles (194 and 196) indicate the projected near field outputbrightness corresponding to any point along guide (bar or plate) length168 just outside the physical boundary of the illustrative polycarbonatemedia, n=1.59. Spatial profile 199 represents the behavior when inputlight begins with a widened +/−57-degree cone in air.

FIG. 5C shows the corresponding spatial light profiles (200 and 202)that arise on flat plane bottom side guide surface 186 for twoillustrative input light conditions within guide 100 or 112, lighttransmitting with a +/−52.6-degree cone in the plane of thecross-section (profile 200) and light transmitting with a+/−38.97-degree cone in the plane of the cross-section (profile 202).The corresponding spatial profiles indicate the projected near fieldoutput brightness corresponding to any point along guide (bar or plate)length 168 just outside the illustrative polycarbonate media, n=1.59.

Spatial light distributions (e.g., 194, 196, 199, 200, and 202) recordthe relative near field brightness uniformity of the illuminationprovided by the tapered light guide in the present example, and can givean indication of the guide's aperture appearance when viewed directly(from above or below). The narrower the angular width (extent) of inputlight provided within the guide's cross-section, the more skewed is theappearance of its light output to the tapered (right hand) end of theplate, producing a dark zone (or band) closest to the source of lightinput. Conversely, input light cones wider than +/−53 degrees within theguide cross-section give rise to progressively more aggressive earlyemission and the corresponding appearance of a bright zone (or band) inthe vicinity of the guide's input face 128.

This more impulsive behavior is illustrated in FIG. 5B by profile 199for +/−57 degree input light (in air) to show one example of the strongeffect that can occur when the angular extent of the input light isimproperly arranged, for the guide's tilted topside plane 184. Eventhough the +/−57-degree input cone is only +/−4 degrees larger than the+/−53 degree cone giving rise to relatively uniform light distribution194, all the higher light angles extract immediately, and give rise to asizeable brightness peak. The wider the input angular cone, the moresevere the bright region becomes, and the darker the guide's tailsection output becomes. Despite such changes to near field apertureappearance, far field beam profiles 180 and 182 can remain reasonablyunaffected.

Equally impulsive non-uniformity is observed for the more narrowlyconfined +/−38.97 degree input light, as revealed by spatial lightdistributions 196 (top side, FIG. 5B) and 202 (bottom side, FIG. 5C). Inboth cases, the more collimated input light within the guide delays theoccurrence of output and is associated with a visibly dark region in thevicinity of input face 128. Although the tapered guide eventuallyachieves a region of spatial brightness uniformity, this region onlyoccurs in the second ⅔rds of the guide length. The narrower the inputangular cone, the more extensive the input end dark region becomes.

The significance of the differences between spatial light distributions194, 196, 199, 200, and 202 as represented in FIGS. 5A-B is that theyreveal a dependence between the uniformity of the light guide's outputbrightness and the angular width of input coupled light. The profiles194 and 200 indicate that spatial uniformity is achieved over the entireguide length in this particular example when input light is held to anangular extent of about +/−53 degrees (in air, just outside theillustrative polycarbonate medium).

It is impractical to derive an analytical equation for the input angularextent corresponding to widest output uniformity, as this result dependson the guide's specific boundary conditions and on the complex Fresnelreflections that arise because of them (and the refractive index of theguiding medium). One example of an optimization method for a differenttapered light guide structure is the stochastic, non-sequential opticalray trace performed noting the input angular extent that gives rise tothe widest and smoothest region of output uniformity that is possiblefor the prevailing materials and their geometric parameters.

Accordingly, best practice of this disclosure arises when the angularextent of input light 146 coupled just inside the tapered light guide'scross-section (as in the example of FIG. 3E) gives rise to substantiallyhomogeneous near-field brightness uniformity illustrated by profiles 196in FIG. 5N and profile 200 in FIG. 5C.

Far field output beams 180 and 182 are composed of the ensemble ofindividual light rays that have failed conditions for total internalreflection at the corresponding surface planes 184 or 186 within taperedlight guide. Total internal reflection behavior is illustrated morecompletely in FIGS. 6A-6B, for light guide sections taken relativelynear input face 128, and for ray trajectories at or near the prevailingcritical angle for the polycarbonate guide medium being illustrated.Similar behavior is illustrated when the guide medium is PMMA or anothersuitably transparent optical material.

The effects of adding a specular reflecting mirror plane (274 or 275)just beyond the tapered light guide's tapered boundary surface 184 orjust beyond the tapered light guide plane boundary surface 186 areillustrated in FIGS. 7A-7C and 8A-8D for the example of a polycarbonateguide medium and dielectric bounding layers existent between guide andmirror plane that are either air or PMMA.

FIG. 6A illustrates the optical paths taken by a single paraxial testray undergoing total internal reflection inside a tapered light guide.The ray path of single illustrative ray 206 from symbolic input source208 is traced from its point of entry just inside input face 128 of thelight guide's the refractive medium (i.e., polycarbonate, n=1.59, in thepresent example). Illustrative ray 206 strikes plane surface 186 atpoint 210, making critical angle 212 (θ_(c)=Sin⁻¹[1/n]) with surfacenormal 214, which is 38.97 degrees for the polycarbonate light guidemedium of the present example. This ray 206 makes a total internalmirror reflection about surface normal 214 and is redirected towardspoint 216 on tilted plane surface 184 (tilted 3 degrees from horizontalin this example) as total internally reflected ray segment 218.Accordingly, the surface normal 220 at point 216 is tiltedcorrespondingly by 3 degrees with respect to plane surface normal 210,and because of this, ray 218 arrives 3 degrees short of the criticalangle 222. Since ray 218 arrives with an angle of incidence less thatthe critical angle, it refracts as output ray segment 224 into thedielectric medium (air in the present case) surrounding therepresentative light guiding cross-section according to Snell's Law. Ray218 is said to fail the condition for total internal reflection at point216, and as such refracting ray segment 224 is extracted as outputillumination within far field output beam 180 as was shown previously inFIG. 5A. This illustrative TIR failure is not 100% efficient because ofthe refractive index discontinuity that exists between the surroundingmedium air and polycarbonate in this example, which gives rise to aFresnel reflection at point 216 as reflected ray segment 226.

Fresnel reflections of this sort are conventionally calculated using theFresnel equations for reflection and transmission coefficients of theorthogonal (parallel and perpendicular) electric field components of anelectromagnetic wave, which are provided in most standard textbooks onelectromagnetic waves (for a more rigorous discussion, see for example,Jenkins and White, Fundamentals of Optics, 4E, McGraw-Hill, Section25.2.) In the present example, light is un-polarized, and ray tracesimulations assign proper light flux to each ray depending on itscomplex angular direction and the prevailing surface boundary conditionsaccording to an incoherent average of the two electromagneticpolarizations, as in equations 2 and 3, where θ_(i) and θ₁ are therespective angles of incidence and transmission with respect to theprevailing surface normal from Snell's Law. The closer the angle ofincidence becomes to the critical angle, θ_(c), at any surface boundarylike point 216 in FIG. 6A, the larger is the amount of light fluxcontained in the Fresnel reflected rays. If light flux in totalinternally reflected ray segment 218 of FIG. 5A is 1 lumen, about 0.815lumens are transmitted into air (81.5%) as ray 224 and 0.175 lumens arereflected at point 216 (17.5%) as ray 226. The splitting ratio betweentransmitted and reflected rays changes according to the angles ofincidence involved.

$\begin{matrix}{R_{AVE} = {0.5\left( {\frac{{Tan}^{2}\left( {\theta_{i} - \theta_{t}} \right)}{{Tan}^{2}\left( {\theta_{i} + \theta_{t}} \right)} + \frac{{Sin}^{2}\left( {\theta_{i} - \theta_{t}} \right)}{{Sin}^{2}\left( {\theta_{i} + \theta_{t}} \right)}} \right)}} & (2) \\{T_{AVE} = {0.5\left( {\frac{4\;{{Sin}^{2}\left( \theta_{t} \right)}{{Cos}^{2}\left( \theta_{i} \right)}}{{{Sin}^{2}\left( {\theta_{i} + \theta_{t}} \right)}{{Cos}^{2}\left( {\theta_{i} - \theta_{t}} \right)}} + \frac{4\;{{Sin}^{2}\left( \theta_{t} \right)}{{Cos}^{2}\left( \theta_{i} \right)}}{{Sin}^{2}\left( {\theta_{i} + \theta_{t}} \right)}} \right)}} & (3)\end{matrix}$

When Fresnel reflected ray segment 226 reaches point 230 in FIG. 6A, itsangle of incidence has moved further away from critical angle 212 as aresult of the reflection at tilted mirror plane 184. Its angle ofincidence with respect to dashed surface normal 214 is about 33 degrees,which is the critical angle, 38.97 in this case, minus two sequential3-degree angular reductions, one occurring on arrival at point 216 andthe second occurring on arrival at point 230. In this instance, theaverage transmission and reflection coefficients correspond totransmitted ray segment 232 contributing about 0.16 output lumens andFresnel reflected ray segment 234 containing about 0.02 lumens.Subsequent internal Fresnel reflections show diminishing contributionsas ray segment 238, 240 and 242 at points 236 and 242. The 1 lumen ofinitial light flux assumed in single illustrative probe ray 206contributes about 0.84 lumens (84%) to far field beam 180 and 0.16lumens (16%) to far field beam 182 in FIG. 5A.

The asymmetric flux splitting (as indicated by the net from an ensembleof the single-ray results illustrated in FIG. 6A) favoring contributionsto the upper far field beam 180 is significant only for this particulartype of single ray path, initially incident at (or near) point 214 andat incident angles at (or near) the critical angle for the guidingmedium used.

FIG. 6B illustrates the optical paths taken by a single paraxial testray undergoing total internal reflection inside a tapered light guide,choosing a slightly different start trajectory than the one shown inFIG. 6A. FIG. 6B traces the corresponding behavior of illustrative inputray 250, which arrives at point 214 with an angle of incidence 3 degreesgreater than illustrative ray 206. The internal transmission path of ray206 from FIG. 6A is shown as dotted for purposes of comparison.Accordingly, ray 250 in exceeding critical angle 212, makes a totalinternal reflection about surface normal 214 and is redirected towardstilted mirror plane 184 as ray segment 252, reaching it at shifted point254. Because the tilt of plane 184 in this example is 3 degrees and ray250 exceeded critical angle 212 by 3 degrees, ray 252 arrives at point254 with an incidence angle exactly equal to critical angle 212, andbecause of this, makes an efficient total internal reflection withessentially all its original flux remaining in reflected ray segment 256(i.e., no light transmission into the surrounding medium, illustrativelybeing air).

When ray 256 arrives at point 258, however, it has gained another 3degrees relative to the prevailing surface normal and as such falls 3degrees inside the critical angle. In this instance, the condition fortotal internal reflection is not satisfied, and refracted ray 260 istransmitted into the surrounding medium (air, in this example). As inthe case of ray 226 above, there is a Fresnel reflection at point 258,reflected ray segment 262 heading towards point 264 on surface 184.Arrival at point 264 also involves refractive transmission into thesurrounding medium as ray segment 266 and another Fresnel reflection,ray segment 268 along with transmitted component 272 at point 270.

Notice that in this example of FIG. 6B, despite being so close instarting trajectory to that in FIG. 6A, the majority of transmitted fluxis contained within output beam 260 (FIG. 6B) on the lower (or flatplane) side of light guiding cross-section. In fact, the output fluxcontributions (shown emboldened in both FIGS. 6A and 6B) are nearlyidentical, except for their side of escape. Other illustrative raytrajectory examples, if chosen, would be seen to cause a wide variety ofintermediary flux distributions between outputs from surface 184 and186.

When all rays within the angular extent of symbolic input light source208 are superimposed on each other, as in FIG. 5A, the average outputflux resulting on each side of bare light guide are contained in theequally energetic far field output beam profiles 180 and 182.

A specularly reflecting mirror-plane on one side of the tapered lightguide (or the other) is used to redirect light flux from one side of thelight guide to the other, so that effectively all extracted light ismade available through a solitary output aperture. The development ofthis basic behavior is illustrated by the same means in FIGS. 7A-7C.

FIG. 7A shows the effect on net output light extracted when adding atilted reflecting plane in air just above the tilted surface of thetapered light guide illustrated in FIG. 5A. When specular reflectingplane 274 (or 275) is placed near (or directly upon) either top orbottom surface 184 or 186 of the representative light guide (100 or112), the corresponding output light extracted from that light guidesurface is forced back into the guiding medium from whence it came by acombination of internal reflections and refractions, becoming a part ofthe collective output beam on the opposing side of the guide from thatof the reflecting plane's location. This behavior is illustrated by theside views of FIG. 7A (for tilted taper plane reflector 274) and 7B (forplane mirror reflector 275). The air-gaps between the light guide mediumand reflector 274 (FIG. 7A) and 275 (FIG. 7B) are 276 and 277respectively (but could in general be any transparent dielectric medium,for example, a medium having a lower refractive index than that of theguide medium itself). In each case, the composite output beam (downwardbeam profile 280, FIG. 7A, and upward beam profile 282, FIG. 7B) isdirected away from the horizontal X-Y plane illustrated by a widerangle, E, 284, than would be expected from either of the intrinsicoutput beam angles (γ_(T) 190 and γ_(P) 192) associated with the2-sided-extractions of FIG. 5A. Both single-sided beam extractionsrepresented by realistic beam profiles 280 and 282 are seen as beingtilted by an additional 8 degrees in the present example over the purelygeometrical expectation. Phantom two-sided beam profiles 180 and 182representing the far field beam profile results of FIG. 5A are includedin dotted form for purposes of comparison. Phantom profiles 282 (FIG.7A) and 284 (FIG. 7B) are the mirror reflections of 180 and 182respectively and each is seen to differ from the actual double-sidedbeam profile phantoms by the taper angle α, which remains 3 degrees inthe present example. Output beam 280 as shown in FIG. 7A projectsdownwards at approximately a 27.5-degree angle, 286, measured fromhorizontal. Output beam 288 as shown in FIG. 7B projects upwards atapproximately a 24-degree angle, 290, also measured from horizontal.Corresponding angles from 2-sided extraction were about 19 degreesdownwards and about 16 degrees upwards (as determined in FIG. 5A).

FIG. 7C shows the effect on light extraction by adding a tiltedreflecting plane that is optically coupled to the tilted surface of thetapered light guide illustrated in FIG. 5A. Air gaps 276 (FIG. 7A) and276 (FIG. 7B) between reflector and light guide plate as used in lightdistributing engines 1 are optional. Contrary to prior art, reflector274 may be applied directly to surface 184 of the representative taperedlight guides without significant compromise in efficiency (assumingreflectivity of the reflecting material is sufficiently high). Reflector274 is applied either by vapor deposition (as in the case of highreflectivity silver or aluminum) or as a separate layer attacheddirectly by means of a thin optical adhesive whose refractive indexnearly matches or is lower than the refractive index of therepresentative polycarbonate light guide material of this example. Adirect reflector attachment method is used to advantage when thereflectivity of reflector 274 exceeds about 95%. One such excellenthigh-reflectivity reflector material available commercially for directattachment is ESR™ as supplied by Minnesota Mining & Manufacturing (3M).3M's so-called ESR™ mirror film material exhibits exceptionally highreflectivity (>0.98) for both polarizations of light over the entirevisible light spectrum regardless of angle of incidence. Elimination ofair-gap 276 in this manner sacrifices only a small amount of total lightoutput in beam profile 300. When ESR™ is separated from tapered lightguide surface 184 by a small air gap, about 95.8% of the input fluxresults in far field output beam 300. When ESR™ is optically coupled tothe plate, as with an index-matching pressure sensitive adhesive, outputconversion efficiency decreases only slightly to about 92%.

FIG. 8A-8D show perspective views of simulated performance for onepossible realistically constructed form of the tapered edge-emittinglight guide pipe introduced earlier. Far field light output in thiscase, as anticipated by the mechanisms illustrated in FIGS. 5A-5C, 6A-6Band 7A-7B above, is well-collimated in one output meridian and not theother as intended, while the output beam is directed obliquely from thelight guide pipe's output aperture plane 126. In this elemental example,plane reflector 274 is applied directly to tapered face 184 of lightguiding pipe 100. Light extracting and redirecting plane reflector 274is configured smoothly for purposes of this example, with lightextracting prisms 104 of light extracting film 102 as shown in FIGS.3A-B given peak angles approaching 180 degrees.

FIG. 8A is a perspective view illustrating the single LED light emitter2 serving as the input portion of the double collimating lightdistributing engine examples of FIGS. 3A-3B and 4, as seen from itsoutput edge 126, for the special case where its light extracting prismsfacets have collapsed to the unstructured form of a smooth mirror plane274. This LED light emitter example comprises single LED emitter 3, precollimating etendue-preserving RAT reflector 14 described above, andlight guiding pipe (bar or rod) 100. Illustrative light guiding pipe 100is made of polycarbonate, but could also be made of any other low-losstransparent optical material including PMMA, Zeonex, and non-absorptiveglasses such as quartz, Pyrex and Boro-silicates. Pipe 100 has a 3 mm×3mm input aperture, and a 57 mm taper length 168 (as in FIG. 5A). Itstaper angle 156 as previously shown (e.g., see FIG. 4), can be about 3degrees, for example. The pipe's top and bottom planes 184 and 186 areflat and parallel. The 3 degree taper is cutoff with a 50-μm thickknife-edge or peripheral edge 158. The RAT reflector's input aperture issized and shaped to match the emission aperture of LED emitter 3, whichis sized 2.4 mm by 2.4 mm so as to receive substantially all the lightfrom a 2×2 array of 1 mm by 1 mm LED chips. Two of many possiblecommercially available 4-chip LED emitters meeting this particularillustrative condition include various configurations of LED emittersmanufactured by Osram Opto Semiconductor under trade names OSTAR™Lighting and Osram OSTAR™ Projection. The RAT reflector's correspondingoutput aperture is made 3 mm×3 mm, so as to match the light guide pipe's3 mm×3 mm input aperture, while also supplying the approximately the+/−52.6 degree angular distribution (in air) associated with the resultsof FIG. 5A-5B.

FIG. 8B provides a topside view of the edge-emitting LED light emitter 2of FIG. 8A, showing the obliquely directed far field beam cross-sectionthat results. The actual computer-simulated far field output beam 310for the example conditions is superimposed accurately in cross-section,and found to make in air a 27 degree angle 312 (as shown) with the lightguiding pipe's output aperture plane 126. This far-field beam'scross-section has about a +/−8 degree angular extent, FWHM (e.g., fullwidth half maximum).

FIG. 8C provides a front view illustrating the light beam cross-sectionthat is emitted from the output edge of the system of FIG. 8B. Thecomputer-simulated far field beam 310 is superimposed accurately in thisdifferent cross-section, and found to make in air the unmodified53-degree out angle 316 that was established by design at the pipe'sinput by RAT reflector 14.

FIG. 8D illustrates the LED light emitter of FIGS. 8A-8C in a topsideperspective view showing the highly asymmetric nature of its obliquelydirected output illumination. As in FIGS. 8B-8C, far field beam profile310 as illustrated was obtained by computer simulation and issuperimposed in its corresponding perspective as emanating from outputedge 126 of light guiding pipe 100 within LED light emitter 2.

Extending the light extraction behavior to the steeper output anglesbetter suited to down lighting can require an additional lightprocessing mechanism within the tapered light guide's underlyingextraction mechanism.

FIG. 9 illustrates the side cross-section of a tapered light guidingpipe 100 (or plate 112) whose tilted (taper) plane 184 is modified toinclude an optical film stack 321 having two different dielectric layers(320 and 322) and a plane mirror 274, with a superimposed simulation ofthe extracted output light's angular cross section. The addition ofoptical film stack 321 introduces an initial step in this importantmechanistic variation for the tapered light guide configuration asillustrated schematically in FIG. 7A. This modification applies equallywhether the tapered light guiding member is a pipe 100 or a plate 112,and whether the guiding material is polycarbonate (as in the ongoingexample, PMMA, or some other optical material such as PMMA having highertransparency). It further applies whether the light guiding plate hasbeen extruded linearly, as in the present example, or extruded radially,as discussed further below (e.g., see FIGS. 34A-34F, 35A, 38A-38B, and39A-39C). The side cross-sectional view of FIG. 9 shows two thinoptically transparent dielectric layers substituted for the air-gap 276as shown in FIG. 7A. The first of these layers, layer 320, is chosen tohave a lower refractive index than that of the material used to form thelight guiding pipe or plate to which it is coupled. In the example ofFIG. 9, the light guide material is taken illustratively as beingpolycarbonate, n=1.59, and the refractive layer 320 which is attached totilted boundary plane 184, has a refractive index which can be less than1.49. Were the light guide material made of acrylic (poly methylmethacrylate), n=1.49, the refractive layer 320 which is attached totilted boundary plane 184, has a refractive index which can be less than1.41. The second of these layers, layer 322, attached to the first, canhave a refractive index equal to or higher than that of the refractiveindex of the light guiding member (100 or 112). When the light guide ispolycarbonate, layer 322 can have a refractive index greater than orequal to 1.59, and when the light guide layer is acrylic, layer 322 canhave a refractive index greater than or equal to 1.49. Reflector plane274 is applied directly for this example to the upper surface of layer322. Layer 320 may be any optically transparent material having arefractive index between about 1.35 and 1.55, whose thickness can beless than 100 μm, but may range upwards from as little as about 50 μm.In practice, layer 320 can be made of an adhesive material formulatedfrom acrylic (poly methyl methacrylate), refractive index between 1.47and 1.49 when the light guide is made of polycarbonate and between 1.39and 1.41 when the light guide is made of pure acrylic (e.g., seeAdhesives Research Inc, Philadelphia, Pa.). Layer 322 can be made of thesame material as light guide (100 or 112) in practice, but may also beany polymeric or glass material with equal or greater refractive indexthan that of the light guide. The thickness of layer 322 is can be lessthan 250 μm, but may range upwards from about 50 μm to thousands ofmicrons and more depending on the intended purpose. FIG. 9 also shows,in cross-sectional view, one possible far field beam simulation 318 thatresults from transmission of input light 208 through the tapered lightguide (100 or 112) right up to reflector plane 274, and just inside thedielectric medium of layer 320.

FIG. 10, is based on a set of computer ray-trace simulations, and plotsout the quantitative relationship existing between the refractive indexchosen for transparent dielectric layer 320 and the internal far fieldbeam angle that results in transparent dielectric layer 322 just beforeplane reflector 274. The internal angle produced using acrylic as layer320 is 24 degrees away from output aperture plane 186. More ideal beamshape is associated with a refractive index value closer to 1.35, whichproduces a far field angle of 33 degrees. The results of FIG. 10 applyto the example using a polycarbonate light guide. A similar trend isobserved when the light guide is made of a lower index material such asacrylic.

The relationship between capture angle and the refractive index ofmedium 320 that is set forth in FIG. 10 indicates that the lower therefractive index of medium 320, the cleaner and narrow is extractedlight beam 318, and the greater is its angle with horizontal. Thesmaller the refractive index difference between tapered light guide pipe(100) or plate (112) and medium 320, the shallower the extraction angleand the more distorted is the extracted beam profile.

Turning the refracted light in layer 322 into a steeper angle thanprovided by its Law of Reflection angle from tilted plane mirror 274requires installing an even steeper mirror angle than that of the lightguide's natural 3 degree taper angle. Rather than doing this by simplyincreasing the steepness of tilt for the entire reflector plane 274 from3 degrees to an angle as high as about 40 degrees, the steeper mirrorcan be Fresnelized as a sequence of substantially identical reflectingfacets, as anticipated earlier by light extraction films 102 shown inFIGS. 3A-3B and 4 above. The process of Frenelizing a thick spherical orcylindrical optical surface shape is standard practice in the opticsindustry as a practical means of reducing an optical element's netthickness (e.g., the field of Fresnel lenses). Its usage is equallyappropriate in reducing the thickness of an otherwise steep plane mirrorsurface. Such is the case with the light reflecting facets that areapplied in this disclosure to achieve more desirable output angles inconjunction with the tapered light guiding pipe 100 and the taperedlight guiding plate 112, and their conjunctive applications.

The basic light extraction mechanism involved, whether applied to thetapered light guide pipe (100) or plate (112) is illustrated by way ofthe cross-sectional view provided in FIG. 11A and the magnifiedcross-sectional view of FIG. 11B for material and geometric values ofthe ongoing example. In this example, both the tapered light guide andfaceted dielectric layer 322 are made of polycarbonate, refractive index1.59, and dielectric coupling layer 320 is made of an optically clearacrylic adhesive, refractive index 1.49. Left side apex facet angle,β_(L), 350 and right side apex facet angle β_(R), 352, are illustratedin the magnified detail of FIG. 11B. They are respectively, 38 degreesand 60 degrees in the present example, but many other suitableillustrative combinations will be established. The array offacetted-prisms is a regular one in this example, but a wider variety ofprism compositions may be blended into a more complex array for specialapplications. And while the basic light extraction mechanisms apply tolight guiding pipes 100 and light guiding plates 112, they also apply tolight guiding disks formed by rotating the tapered cross-section of FIG.11A about an axis parallel to input face 128.

FIG. 11A shows the underlying behavior by tracing the path of oneillustrative light guiding probe ray 330 (plus sequential segments 332,334 and 336), and also by showing the resulting redirection of thecollective far field output beam 336 representing an ensemble of alloutput rays.

Full extraction of internal beam 330 from generically tapered lightguide pipe (100) or plate (112) while simultaneously changing beamdirection can be achieved in cross-sectional view with facettedredirection layer 102 which is composed of a sequential series of lefthand and right hand reflective facets (340 and 342) made in layer 322placed just above lower index layer 320, as shown in the side view ofFIG. 11A. The asymmetric facets 340 and 342 are formed, for example, ina clear polymeric medium such as polycarbonate, and surface-coated withmetallically reflective, pinhole-free film, such as silver, which alsocould be aluminum or another high-reflectivity coating.

By this design, light extraction occurs predominately, if notexclusively, on right hand facets 342 in this arrangement. Extractablerays such as 4240 in tapered light guide 4100 pass through low indexlayer 4212 (ray segment 4242) and then through facetted medium 4236 (raysegment 4244) along the direction of extracted beam 4210 in FIG. 41A.Redirection occurs by reflection at the tilt of right hand facets 4234,as illustrated for one facet in FIG. 42A. Redirected beam 4246 containsray segment 4248 along with all other redirected rays surrounding it.

FIG. 11B provides a magnified view 329 of the asymmetric facet geometryapplied in this illustrative example. The total included apex angle 352(β_(T)) is the sum of left hand facet angle 354 (β_(L)) and right handfacet angle 356 (β_(R)), each defined with respect to surface normal 351for the interface 358 between film layer 322 and lower index layer 320.When output light is directed normal to the associated tapered lightguide's output face (126 for pipe 100 and 123 for plate 112), the totalincluded apex angle 352 is about 98 degrees, left hand facet angle 354is about 38 degrees and right hand facet angle 356 is about 60 degrees,as mentioned above for values used in the ongoing. The facet depth 360(FD), along with the respective facet angles determines prism pitch,which is by geometry, FD [Tan (β_(L))+Tan(β_(R))], where FD [Tan(β_(L))] is sub-length 370 and where FD [Tan (β_(L))] is sub-length 372.Redirection of extracted light is controlled predominately (if notexclusively) by the right hand facet angle 342.

FIG. 11C supports this description by showing the correspondingcross-sectional side view of a ray-trace simulation of 500,000 inputrays 208 for this illustrative configuration, plotting every 1000^(th)ray for viewing simplicity. It's easy to see from this presentation thatthe array of right hand facets (342) serve as the source ofdown-directed illumination, while the left hand facets appear only asintervening dark stripes. With these introductory elements as afoundation, some illustrative examples will be given.

The first example will provide additional performance details of thesingle LED form of tapered edge-emitting light bar input engine 120introduced earlier in FIGS. 3A-3E and 4, using facetted multi-layeredlight extraction film 102.

FIG. 12A provides another exploded view of the tapered edge-emittinglight bar input engine 120 clearly showing the construction of itsmulti-layer light extracting, turning and collimating film 102.

FIG. 12B shows a top view of input engine system 120 including its farfield output beam pattern, a +/−6 degree collimated beam 162 that isextracted into air. Also shown is the internally pointing far field beamcross section just inside output aperture 126 of tapered light guidingpipe 100, +/−3.77 degree collimated beam 380. Using the values of theongoing example, as provided above, the output beam from this engine isdirected along the system's X-axis 7. As will be shown further below,different facet angle combinations may yield a wide variety of outputpointing directions other than the axial one.

FIG. 12C shows the information contained in FIG. 12B, but in aperspective view that shows the Z-meridian angular extent 384 of farfield output beam 162, as well as the high degree of comparativeY-meridian angular collimation 386.

FIGS. 12D and 12E are both perspective views of input engine 120 thatshow the near field spatial uniformities 390 and 392 resulting from twodifferent coarsenesses of prism period for prismatic light extractionfilm 102. The finer (smaller) the prism pitch, the finer is theresulting near field brightness non-uniformity.

FIGS. 12F-12H explore this trend clearly from the distinct black andwhite bars of the 57 mm long edge uniformity pattern 390, to the smallerbars in pattern 392, and then to the practically indistinguishable barsof pattern 396, which represents 160 μm prism periods.

FIGS. 13A-13C emphasize the relationship, discussed preliminarily above,existent between the input angular distribution (400, 402 and 404)provided in the X-meridian by RAT reflector 14 coupling LED input lightto input aperture 128 of the tapered light guiding pipe 100, and thenear field spatial uniformity pattern resulting along the tapered pipe's57 mm output length (410, 412, and 414). These results use the 160-μmperiod form of prismatic light extraction film 104, isolated as 406.

Input angular distributions 400, 402 and 404 in air prior to couplingacross input aperture 128 are shown separately as FIGS. 14A, 14C and14D, and are approximately +/−33.6 degrees, +/−52.6 degrees and +/−65.0degrees respectively. The input angular extent that is shown in FIG. 14Bis approximately +/−41 degrees. It is easy to see that the best nearfield uniformity is achieved in FIG. 13B, as a result of +/−52.6 degreeinput light distribution 402.

FIG. 15 is a graphical representation of four illustrative near fieldspatial uniformity profiles, 410, 412, 141, and 416 as a function of thefour angular distributions, 400, 401, 402 and 404 shown in FIGS.14A-14D. The angular distribution patterns responsible for the fourillustrative near field spatial uniformity profiles are superimposed onFIG. 15 emboldened and underlined as 400, 401, 402, and 404.

The second example, FIGS. 16A-16B, shows the conjunctive far fieldillumination patterns that result when tapered edge-emitting inputengine 120 is combined with tapered light guiding plate 112, as shownearlier in FIGS. 3A-3E and FIG. 4, but with the finer pitch (period)prismatic light extraction film shown above. The distance between thisthin-profile illumination system 1 and the 1800 mm×1800 mm far-fieldsurface illuminated is 1500 mm.

FIG. 16A shows a perspective view of the geometry involved, includingthe computer simulated far field beam pattern that results. Theillustrative 57 mm×57 mm×3 mm dimensions of illumination system 1, thecomplete system noted as 430 in this example, is rendered exactly toscale with respect of the 1800 mm×1800 mm length 436 and width 438 ofthe surface 440 to be illuminated from a height 442 that's 1500 mm away.

FIG. 16B provides magnified view 444 of the thin-profile doublycollimating illumination system noted at 430 in FIG. 16A.

FIG. 17 is a computer simulated 2D graphic representation of the farfield illumination pattern 450 made on far field surface 440 asilluminated in the perspective view of FIG. 16A. The angular extent ofbeam pattern 450 in this example is approximately between +/−5 degreesand +/−6 degrees full width half maximum (FWHM) in both meridians shown(X meridian along length 436 and Y meridian along width 438. The linewidth profiles in each meridian are shown as the set 452 and the singleprofile 454. White arrow 451 denotes the X meridian line width profilecorresponding to the pattern shown, 450. The other X meridian line widthprofiles correspond to additional simulation runs with different valuesof right hand facet angle 352 (see FIG. 11B). A slight change in the farfield angular pointing direction results from slight changes in thenominally 60-degree apex angle, α_(R).

FIG. 18 is a graphic representation of a set of differently tilted farfield beam cross-sections generated by the illumination system of FIG.16A in response to five slightly different choices of facet angleswithin the prisms applied to the surface of its tapered light guidingplate.

This facet-angle means of controlling the illumination system pointingdirection is a very powerful feature of some implementations of thisdisclosure. Flat mounted illumination systems 430 of FIG. 16A can bedeployed to provide various normal and off normal pointing illuminatingbeams and far field patterns with the degree of beam pointing directionset by choosing the extracting film's prismatic facet anglesappropriately.

The spatial overlap of the five far field beams caused by a distributionof the same five choices of facet angles within a single 57 mm×57 mmlight extraction film may be applied to tapered light guiding plate 112,resulting in uniformly widened far field beam profile. For smoother(less discrete) beam distributions, a greater number of facet-anglechoices may be included.

FIG. 19 is a graphic representation showing nine different far fieldbeam cross-sections to demonstrate the +60 degree to −60 degree range ofbeam directions that are accessible by means of varying internal lightredirecting prism angles within the thin-profile light guidingillumination system's light distributing plate 112. FIG. 19 shows thepower of this means of facet-angle tailored angle spreading for the ninewidely different far field beam directions (500, 502, 504, 506, 508,510, 512, 514, and 516) each created in the X meridian about systemsurface normal 441 by merely changing the right hand facet angles(β_(R)) in the 57 mm×57 mm light extraction film 480 of the presentexample as referenced by the arrangement shown in the perspective viewof FIG. 16B.

FIG. 20 contains a graph of prismatic facet angles within lightextraction and turning film versus the far field beam-point angle itcreates, for the thin-profile light guiding illumination system of FIG.3A. While the functional relationship expressed in FIG. 20 is for thepolycarbonate light guiding plate 112 of the present example, a similarfunctional relationship exists for other material combinations such theone associated with an acrylic light guiding plate 112. FIG. 20 revealsthe underlying physical relationship existent between the right handfacet-angle, in degrees from apex normal 441 as discussed earlier, andthe far field beam pointing angle measured from the normal to thesystem's output aperture plane. It is seen that by this method, beampointing may be varied over the full angular range from −60 degrees to+60 degrees. The dotted line in FIG. 20 is a linear fit to the simulateddata and has an intercept value, b=59.5 and a slope value, m=0.309, inthe equation α_(R)=mφ_(P)+b, with φ_(P) being the pointing angle indegrees measured from the system's surface normal.

The far field illumination pattern's angular diversity is expandedwithin this disclosure in several other ways, applied separately or incombination. A first means of output angle control, mentioned earlierwith regard to the implementation of FIG. 1D, involves use of one or twooutput light conditioning layers 52 and 54 in the form of a lenticulartype of angle-spreading diffusers. The second means of output anglecontrol involves use of collimated edge light sources whose degree ofinput collimation may be adjusted in a way that alters the angularextent of far field illumination (as described above as in FIGS. 2A-2C.The third means of output angle control involves the variation on thedistribution of prism facet structures within the light extractingredirection layer as shown just above.

Of these approaches for widening the illumination system's angularextent beyond the nominally +/−5 degrees illustrated above, adding oneor two angle-spreading diffuser sheets (for example, lenticular anglespreading sheets 52 and 54) across system's square or rectangular outputaperture (e.g., as illustrated earlier in FIGS. 1D, 2D and 4) may be themost easily applied, in some implementations. As reasonablywell-collimated light beams of the instant invention pass through anyone or two-dimensional angle spreading diffusing sheet their beamprofile is broadened by the angle spreading mechanism involved.Substituting one set of light spreading films for another makes thedesired changes to the light engine's output light distribution.

Several prior art light diffusing sheets may be used in this manner,including bulk scattering-type diffusers, spherical lenticular type lenssheets, and various diffractive type light shaping diffuser sheets. Yetone particular variation of lighting spreading diffuser sheet, alenticular lens sheet with parabolic lens elements, will be shown ashaving unique attributes.

FIG. 21 is a side cross-section illustrating the computer ray-tracesimulated far field angle spreading behavior of a prior art form of bulkscattering-type diffusing sheet applied in the output aperture of thethin-profile light guiding illumination system of FIG. 3A. FIG. 21superimposes a family of typical diffusively broadened far field beamprofiles 520, shown for visual convenience as being normalized withrespect to their on axis intensity. Each profile actually distributesapproximately the same number of output lumens to field surface 522.Silhouette 524 (shown in black) represents the far field beam profile ofthin-profile illumination system 1 without any external light spreadingdiffusion. Far field beam profiles 526, 538, 530 and 532 areillustrative of the type of beam spreading that is possible, 526 (+/−10degrees), 528 (+/−15 degrees), 530 (+/−25 degrees) and 532 (+/−30degrees). In addition to widening the light emitting engine's angularextent, diffuser 534 also hides a wide variety of inhomogeneities inbrightness uniformity caused by manufacturing defects or toleranceviolations. A system height 540 of 1500 mm was taken for thiscomparison.

Luminit LLC of Torrance, Calif. (formerly Physical Optics Corporation)manufactures one line of diffractive light diffusing sheets made forthis purpose. Their commercial light-shaping diffusers scattercollimated input light (by means of holographic diffraction)predominately in the forward direction, with a wide range of selectableangular cones (e.g., +/−10 degrees, +/−15 degrees, +/−20 degrees, +/−30degrees and +/−40 degrees in circularly symmetric cones, and +/−5degrees by +115 degrees, +/−5 degrees by +/−20 degrees, +/−5 degrees by+/−30 degrees, +/−17.5 degrees by +/−37.5 degrees, +/−17.5 degrees by+/−47.5 degrees and +/−30 degrees by +/−47.5 in asymmetric cones).

Other conventional diffuser sheets 534 that can be used in this samemanner within this disclosure include, whether individually or incombination, adhesive resins or polymer sheets loaded with scatteringpowders such as for example titanium dioxide or fluorescent oxides,clear plates coated with opalescent or fluorescent material, androughened sand blasted glass or plastic plates.

Another way of widening the nominally +/−5 degree angular extent outputis by adding one or two spherical lenticular lens sheets across thelight emitting engine's output aperture. Lenticular lens sheets are thintransparent elements formed by a linear array of nominally identicallenses. Lenticular lenses in the prior art are most commonly sphericalones, but have also been prismatic. For example, see the schematiccross-sectional side view in FIG. 22A and the perspective view of FIG.22B.

Other prior art light spreading diffuser examples have includedtwo-dimensional arrays of micro lenses and two-dimensional arrays ofpyramidal cones. However, most of the associated prior art teaching hasbeen concerned with using such micro lens sheets for near field lightdiffusing applications such as homogenizing and expanding the angularcone of the general back illumination provided by so-called backlightsto the rear side of directly viewed liquid crystal display (LCD)screens, as in cell phone displays, laptop computer displays and desktop monitor displays, not large area lighting or illumination.

One company, RPC Photonics of Rochester, N.Y. produces a line ofEngineered Diffusers™ using various mathematically developedtwo-dimensional distributions of micro-sized lenslets of considerableshape diversity (see topographic schematic representation of a typicalsurface region for this type of diffuser in FIG. 22C). In this case, theclear optical lens sheet material has a pebbled morphology composed ofnominally 1-100 μm, sized lens elements varying from the steeper-walledcone-like shapes 600, and spherical shapes 602, to even distortedspheroids 604 and 606. Tooling masters for such complex microstructuresare laser written in photo-resist and then delineatedphotolithographically. Commercial RPC Photonics products are made bycasting and curing, by compression molding and by injection molding.Such distributed lens light shaping diffuser products could be designedfor effective use as an angle spreading diffuser sheet 534. Thepebble-lens Engineered Diffuser™ approach provides convenient means torealize a much wider range of far field light distributions from thewell-collimated light-emitting engine than with any other prior artlenticular type micro lens sheet approach.

While this method may be applied to some implementations of lightemitting engines, a simple variation of the lenticular-type anglespreading lens sheet has been found that is less costly to fabricate andhas an equally customizable light-spreading performance as compared withthe more expensive and complicated approach of FIG. 22C.

Since the far field output beams from illumination systems 1 areintrinsically well collimated in two orthogonal meridians, lesscomplicated lenticular sheets or films can be used and still achievecustomizable results similar to these achievable by the approach of FIG.22C. While some applications may benefit from the implied randomness ofpitch in this approach, the simpler stripe-like lens elements of alenticular sheet, with stripe axes made orthogonal to the plane orplanes of collimation, may be quite sufficient, yet far cheaper, for thevarious best mode light distributions needed in down and wall lightingapplications.

Manufacturing processes for lenticular lens sheets are readily availableand offer lowest possible manufacturing costs. Lenticular sheets can beformed by low-cost plastic extrusion because of their longitudinallygrooved nature. In addition, 3M's prolific brightness enhancing filmproducts (e.g., BEF-T™) are lenticular structures of nominally 50 μmwide Porro prism grooves with internal prism angles being 45 degrees, 90degrees and 45 degrees. Such prism sheets are routinely manufacturedtoday by high volume roll-to-roll acrylate-based casting and curingprocesses in very high volumes with intrinsically low manufacturing cost(per square foot). The same materials are also readily manufactured byhot embossing. Manufacturing qualities of these effectively embossedmicrostructures are best when the lenticular grooves run down the lengthof the processed rolls of the continuously replicated material. Microreplication of features having complex shape variations running acrossthe roll as well as down its length (for example, those of the pebblelenses of FIG. 22C) is feasible, but more difficult to produce on areliable basis. Pebble-type lenses are incompatible with extrusion.

FIG. 22A represents a schematic cross-sectional side view of a prior artform of a cylindrical lens array film containing spherically shaped lenselements known as a lenticular diffuser or lenticular diffuser sheet.The traditional prior art lenticular diffuser sheet, illustrated byschematic cross-section in FIG. 22A, is an optically transparent film orsheet material 550 made of a polymer or glass composition whose planesurface 552 is formed to contain a micro structured array 554 ofparallel lens cross-sections, each lens cross-section (sometimes calleda lenticule or a lenticular) having generally identical cross-sectionalshape 556, SAG 558 and a corresponding pitch or repeat-period PER 560.When the individual lens cross-sections 562 are concave or convexportions of a spherical (or aspheric) cylinder lens, the SAG and the PERare related by simple geometrical expression given in equations 4-7,equation 6 representing the SAG for classical spherical curvature, andequation 7 representing the SAG for a classical aspheric curvature(including all possible polynomial shapes, comprising ellipses,parabolas, hyperbolas, and conic sections). In most cases SD=PER/2, andspecifies one half of the lens period PER, RLEN representing theassociated radius of curvature, CC representing the conic constant(traditionally −1 for parabolic curve, 0 for a sphere, >1 for ellipticalcurve, and >1 for hyperbolic curves), and A1L, B1L, C1L and D1Lrepresenting the first through fourth aspheric coefficients.KK1L=(SD)² /ABS(RLEN)  (4)KK2L=((SD)/ABS(RLEN))²  (5)S00=KK1L/[1+SQRT(1−(1+CC(KK2L))]  (6)))SST=S00+(A1L(SD ⁴))+(B1L(SD ⁶))+(C1L(SD ⁸))+(D1L(SD ¹⁰))  (7)

FIG. 22A shows that ideal illustrative collimated rays 564 or 566 passthrough diffuser sheet 568 parallel to surface normal 580 and arerefracted by the optical power of the individual lens elements 556 inthe array 554 through the corresponding focal points 570 or 572. Theserefracted light rays then diverge with increased angular extent 574 or576 that, to only rough paraxial approximation, is a predictablefunction of the lens' characteristic focal length. Paraxialapproximations are unreliable because they represent a very smallfraction of the total volume of realistic rays involved, because totalinternal reflections may occur within the sheet, and because estimationof the collective skew ray transmissions through an asperhically shapedelement is extremely challenging, and is generally only addressed bycomputer based ray tracing.

In addition to this, the prior art stands notably silent on thepractical distinctions between far-field illuminating results associatedwith collimated rays first striking the plane surface 574 of lenticularlens sheet 568 and those first striking the curved lens surfaces 562.While both orientations produce useful results for some illuminationapplications, the results are in fact strikingly different in quite afew cases, not only in effective transmission efficiency, but also inthe far-field light distributions themselves. And, these differenceswill be shown of significant value when practicing some of theimplementations of this disclosure.

Commercially available lenticular lens sheets are primarily spherical intheir lens cross-sections and made for use as near field 3D imaging lensoverlays on top of suitable images (sized from inches on a side to manyfeet on a side). They also are used for decorative visual effects on awide variety of packages. One typical manufacturer of lenticular sheetsis PACUR of Oshkosh, Wis. Their lenticular sheet products are made byembossing polyester resin with 40-100 lens elements per inch,corresponding to lenticular widths of PER=0.251 mm to PER=0.635 mm, andlenticular radii of 0.251 mm to 0.371 mm. Lenticular sheets are alsomade of acrylic and polycarbonate. Other manufacturers include forexample, Human Eyes Technologies Ltd. Jerusalem, Israel, Micro LensTechnology (Indian Trails, N.C.). In imaging applications of lenticularlens sheets, the planeside 574 of the lenticular sheet 568 is laminatedonto the image layer and reflected light passes outwards through thelenses towards the viewer. The imaging (or viewing) properties oflenticular products cannot be used to predict the effects on far fieldillumination.

Reliable descriptions of a lenticular diffuser's actual angle wideningeffects on far field illumination, even those commercially available forother applications, are only possible by direct experiment and, as inthe present example, by lab validated computer simulation. When properlyimplemented, computer simulations of a lenticular lens sheet's opticalperformance duplicate the results of reference laboratory experiments,and enable discovery of new and useful lenticular implementations.

As an example of a spherical lenticular prior art example that doesagree with paraxial theory, we present the far field illuminationperformance of one of the lenticular products with used in commercial 3Dimaging: PACUR's LENSTAR 3D. It has 100 lenticulars per inch, alenticule radius 4527 of 0.0092″ (0.23368 mm) and a lenticule width(PER) 4512 of 0.0101″ (0.25654 mm). The associated SAG 558 is 0.3835 mm,and the implied focal length (572 in FIG. 22A) is 0.5842 mm. This focallength predicts a far field illumination cone by the thin lens paraxialapproximation of +/−12 degrees (24 degrees full angle). PACUR reports a30-degree field of view in imaging mode applications.

FIG. 23A and FIG. 23B show the far field behavior for collimated+/−5-degree input light provided by doubly collimating light emittingsystem 1 as described earlier, or any other similarly collimated lightsource. FIG. 23A shows the result when the lenticulars point away frominput light 650, and FIG. 23B shows in this case the very similarresults when the lenticular vertices point towards input light 650. Inboth cases the effective transmission efficiencies are about 92% and theangular extents 652 (and 653) of the respective far field lightdistributions are +/−12 and +/−10 degrees respectively, FWHM as shownfrom the associated beam silhouettes 654 and 656. The far-field beamprofile half width 658 is designated in each case.

Far-field illumination results with lenticular diffusers are only aspredictable as this when the lenticular cross-sections are thinspherical shapes. When the lenticulars become aspheric and sag moredeeply, the paraxial approximation breaks down, and simple performancepredictions prove unsatisfactory. Computer simulations are required insuch cases to obtain reliable performance predications.

The actual behavior of aspheric lenticulars within the context of thisdisclosure is demonstrated by the following set of examples comprisingshallow parabolic lenticulars, deeper parabolic lenticulars, prism-likehyperbolic lenticulars, mixed lenticulars and crossed (orthogonal)lenticulars. These examples uncover unique differences in lenticularillumination characteristics, unanticipated by prior art. The examplesshow that effective practice of this disclosure can optionally depend onnot only the selection of certain ranges of lenticular designparameters, but also on the lenticular orientation with respect to inputlight. The behavioral differences are quite striking, and lead to asubset of useful illumination profiles and patterns accessible withinthis disclosure.

FIG. 24A provides perspective view of a typical parabolic (orhyperbolic) lenticular diffuser sheet 690 having parabollically-shapedlenticular elements. FIG. 24B shows the round-bottomed far field beamcross section that results when +/−5 degree×+/−5 degree collimated lightas from the light emitting system of FIG. 3A is applied to the planeside of a lenticular lens sheet having parabollically shaped lenticularelements with a relatively shallow sag. The lenticular elements 696 inFIG. 24A differ from those in FIG. 23B in that they are non-spherical incross-section and are somewhat more deeply sagged.

FIG. 24C shows the flat-bottomed far field beam cross section thatresults when +/−5 degree×+/−5 degree collimated light as from the lightemitting system of FIG. 3A is applied to the lens side of a lenticularlens sheet having parabollically shaped lenticular elements with arelatively shallow sag.

FIGS. 24B-24C illustrate the side elevations of a parabolic lenticularhaving peak to base ratio, SAG/PER=0.2. The parabolic focal point forthis condition is about 0.62 mm. Far field representations of the inputand output light are shown in silhouette above and below the lenticularsheet. When collimated input light 650 first strikes plane surface 692of the lenticular sheet 690, the resulting far-field output beamsilhouette 700 is symmetrical with angular extent 702 being+/22 degreesFWHM as shown. The corresponding center-weighted illumination pattern ona surface 1.5 m below the lenticular sheet has a width at half peak 4534of about 1.2 m, in close agreement with the silhouette's+/−22 degreeangular extent 702. For this orientation, the processed illuminationdisperses outwards from its central peak over a 2.6 m wide area 1.5 mbelow, as shown. When collimated light 650 first strikes lenticularsurface 698, however, a quite differently shaped beam profile (and fieldpattern) results. While the FWHM angular extent 708 remains about thesame, the output beam silhouette 710 has a flat-bottomed triangularshape that produces a square (or rectangular) field distribution withsharp angular cutoff. The resulting flat-topped field profile deploysalmost all output lumens within a 1.2 m wide region 1.5 m below. Thissharp cut-off behavior bares strong resemblance to the light emittingengine implementations employing RAT reflectors by themselves, and isequally useful, in some implementations. In both orientations of thislenticular sheet 690, the effective transmission efficiency is about92%.

FIG. 24D shows the wider-angled round-bottomed far field beam crosssection with satellite wings that results when +/−5 degree×+/−5 degreecollimated light as from the light emitting system of FIG. 3A is appliedto the plane side of a lenticular lens sheet having parabollicallyshaped lenticular elements with a moderately deep sag.

FIG. 24E shows the wide-angle flat-bottomed far field beam cross sectionthat results when +/−5 degree×+/−5 degree collimated light as from thelight emitting system of FIG. 3A is applied to the lens side of alenticular lens sheet having parabollically shaped lenticular elementswith a moderately deep sag.

FIGS. 24D-24E illustrate the side elevations of a parabolic lenticularhaving a somewhat larger peak to base ratio, SAG/PER=0.5. The parabolicfocal point for this case is about 0.25 mm. When collimated input light650 first strikes plane surface 692 this time, the far-field beamsilhouette 730 is practically unchanged in appearance, +/24 degrees FWHMas shown, but transmits only 51% of input light 650 in its main outputlobe 730. A portion of the remaining 49% is output in the weak highangle rabbit ear pattern shown, with the remainder trapped inside thelenticular sheet by total internal reflections, some back reflectedtowards the input source. The illumination pattern that results is alsoabout the same as that shown for the shallower parabolic lenticulars inFIG. 24B. No such breakdown occurs when collimated input light 650 firststrikes the deeper parabolic lenticulars 734. The deeper paraboliclenses nearly double the far field angular extent from +/−22 degrees inFIG. 24C to +/−42 degrees in FIG. 24E. Moreover, the output beamsilhouette retains the flat-bottomed triangular cross-section it showedin FIG. 24C along with the correspondingly sharp angular cutoff. And,despite the considerably widened angular extent, transmission efficiencyis not compromised, remaining at 92%.

FIG. 24F shows the wide angle tri-modal far field beam cross sectionthat results when +/−5 degree×+/−5 degree collimated light asillustratively from the light emitting system of FIG. 3A is applied tothe plane side of a lenticular lens sheet having parabollically shapedlenticular elements with a very deep sag.

FIG. 24G shows the very wide angle far field beam cross section thatresults when +/−5 degree×+/−5 degree collimated light as illustrativelyfrom the light emitting system of FIG. 3A is applied to the lens side ofa lenticular lens sheet having parabollically shaped lenticular elementswith a very deep sag.

FIGS. 24F-24G illustrate the corresponding diffusive properties of aneven deeper parabolic lenticular design, one having a peak to baseratio, SAG/PER=1.0, twice that of the example shown in FIGS. 24D-24E.The parabolic focal point for this ratio is about 0.125 mm. When inputlight 650 first strikes plane surface 692, the effects from totalinternal reflections shown in FIG. 24D continues, with transmissionefficiency improving slightly from 51% to about 70%, but with the outputbeam's cross-section 806 becoming strongly tri-modal showing threedistinct illumination peaks in the far field illumination pattern.Tri-modal light distributions may be used to spot light (or flood light)a central location and two satellites. The far field behavior shown withthe lens up lenticular orientation in FIG. 24G demonstrates that sharplycutoff even illumination 820 is possible with this lenticular diffuser808 out to 120 degrees full angle without compromise. Despite so wide anangular cone 813 where some refractive recapture of higher angle outputlight by neighboring parabolic lenticulars is inevitable, nettransmission efficiency only drops to 86% and output light continues toshow the characteristic flat-bottomed triangular beam silhouette 820associated with such lens up lenticular orientation.

FIG. 25 is a graph summarizing the geometric relationship found to existbetween total far field angle φ870, (measured FWHM 872) and theparabolic lenticular peak-to-base ratios (SAG/PER) between 0.1 and 1.0,for lenticular diffuser sheets 874 of all types. These results occuronly for the special case when the lenticular curvatures are made toface towards collimated input light 650. The applicable peak-to-baseratio range, 876, is considered unique in that net transmissionefficiency remains above 86% throughout, and is 90% or greater betweenSAG/PER=0.1 and SGA/PER=0.75. Far field beam cross-sections, representedby silhouettes in FIGS. 24C, 24E, and 24G, maintain their substantiallyflat-bottomed triangular characteristics throughout the entire range aswell.

The functional relationship graphed in FIG. 25 is non-linear and notpredicted mathematically by any simple theory. A reasonable linearapproximation is provided approximately in equation 8 for lenticulardiffuser sheets made of polymethyl methacrylate (acrylic), n=1.4935809,and in equation 9 for sheets made of polycarbonate, n=1.59. Lenticulardiffuser sheets 874 used may be made of any suitable opticallytransparent polymeric (or glass) material, but those with refractiveindices nearer to that of acrylic are better at suppressing transmissionlosses due to total internal reflection. Lenticular diffuser sheets 874made of polycarbonate, n=1.59, are better at achieving wider far fieldangles at smaller peak-to-base ratio. One example of this is differenceis that a parabolic lenticular made of acrylic achieves a far fieldangular extent of 120 degrees full angle with a peak-to-base ratio,SAG/PER of about 0.63, whereas its polycarbonate counterpart does sowith a SAG/PER of about 0.525, which reduces the necessary parabolicaspect ratio by about 20%. The cost of this particular comparison isonly about 2% in net transmission efficiency, which is probablyinconsequential for most applications.φ=172.24[SAG/PER] ^(0.38)−48.5(8)  (8)φ=203.15[SAG/PER] ^(0.45)−46.66  (9)

It is important to point out that hyperbolic lenticulars of any designdo not develop the favorable flat-bottomed triangular far field beamcross-sections of FIGS. 24C, 24E, and 24G whether their lenticularspoint towards the source of collimated input light 650, or away.

FIG. 26 shows a perspective view of thin profile illumination system 1along with one sheet of lenticular angle spreading film 874 with itsspreading power in the X meridian, its lenticules facing towards theincoming lighting from light guiding plate subsystem 110, as suggestedby the findings of FIGS. 24C, 24E, 24G and the summarizing graph of FIG.25.

FIG. 27 shows one illustrative result with illumination system 1 of FIG.26 placed at a 1500 mm height above the 1800 mm×1800 mm surface to beilluminated. The computer simulated field pattern 880 is spread about+/−30 degrees along x-axis 7, but remains about +/−5 degrees alongy-axis 5. The center of the 57 mm×57 mm luminaire is shown as 882. Thisresult has been validated experimentally using embossed lenticular filmof the equivalent design.

FIG. 28 shows a perspective view of thin profile illumination system 1along with two orthogonally directed sheets of lenticular anglespreading film 874 (and 875 the same design as 874) with its spreadingpower in the X meridian and in the Y meridian, with both sheet'slenticules facing towards the incoming lighting from light guiding platesubsystem 110, as suggested by the findings of FIGS. 24C, 24E, 24G andthe summarizing graph of FIG. 25.

FIGS. 29A-29B shows two illustrative results with thin illuminationsystem 1 of FIG. 28 placed at a 1500 mm height above the 1800 mm×1800 mmsurface to be illuminated. The computer simulated field patterns 884(FIG. 29A) and 886 (FIG. 29B) are spread about +/−30 degrees along bothx-axis 7 and y-axis 5 in FIG. 29A, and about +/−15 degrees in FIG. 29B.The centers of the 57 mm×57 mm luminaire are shown as 882. These resultshave also been validated experimentally using embossed lenticular filmsof the equivalent design.

Total effective field efficiency for the single-emitter luminaireformat, without use of angle-spreading film, is 0.74 (0.86 for taperedinput bar and 0.86 for tapered plate) with antireflection coatingsapplied to the input aperture of both bar and plate. Field efficiencydrops to 0.67 without input coatings (0.82 for tapered bar and 0.82 fortapered plate). Both types of spreading films (lenticular anddiffractive) have net transmission efficiencies of >0.9, and therebyreduce the system's net field efficiencies by 0.9 for one spreading filmand by 0.81 for two.

Field efficiency for the higher-output multi-emitter luminaire format asdescribed in FIGS. 2A-2C can be better because the output efficiency ofthe array-type light engine is about 10%-15% higher than that of thetapered-bar light engine. Net field efficiency for the higher-outputsystem is 0.82 without use of angle-spreading film (0.95 for thearray-type light engine and 0.86 for the AR-coated tapered plate).

These field efficiencies are quite comparable to the total luminaireefficiencies provided by the traditional 2′×2′ fluorescent troffers usedcommonly in commercial overhead lighting treatments, ranging between 0.5and 0.7 depending on design.

A greater efficiency advantage is realized in task lighting applicationswhere premium value can be placed on lumens delivered to a particularcircular, square or rectangular field area.

While it may be of growing economic and environmental importance toachieve luminaries with higher energy efficiency, it is also importantto enable meaningful reductions in size and weight. Smaller and thinnerluminaries provide lighting architects with new design alternatives, butprovide commercial builders and their lighting installers withpotentially less labor-intensive (and less costly) installationrequirements. Along these lines, it can be advantageous to configuresuch thinner luminaries or illumination devices to fit within therecesses of standard lighting fixtures or fixtures present in a givenenvironment. For example, implementations of lighting or illuminationdevices described below can be light in weight and thin in profile whilehaving radial or XY cross-sectional dimensions that are sized and shapedto fit within a lighting fixture configured to receive a standardizedlight device including, but not limited to, PAR64, PAR56, PAR46, PAR38,PAR36, PAR30, PAR20, and/or PAR16-sized lighting devices. That is tosay, implementations of illumination devices described below can havemaximum radial dimensions that are between 2 inches and 8 inches, forexample, 2 inches, 2.5 inches, 3.75 inches, 4.5 inches, 5.75 inches, 7inches, and/or 8 inches. In this way, implementations provided hereinmay provide higher efficiency lighting devices that may be installed orretrofit within existing lighting fixtures configured to receivedifferently configured illumination devices.

FIG. 30A provides an exploded top perspective view 890 of one example ofa fully configured light engine implementation based on the functionalillustrations of FIGS. 1A-1D, 3A-3E, 4, 16A-16B, 26, and 28. This fullyconfigured light engine form is as also described in U.S. ProvisionalPatent Application Ser. No. 61/104,606. FIG. 30B provides a magnifiedperspective view 892 of the coupling region existent between acommercial LED emitter 904 that can be used, the corresponding square orrectangular RAT reflector 906 and tapered light guiding bar 100 withlight extraction film 102, as was referenced in U.S. Provisional PatentApplication Ser. No. 61/104,606. The core light generating sub-system900 includes illustrative heat sink element 902, commercial 4-chip LEDemitter 904 (OSTAR™ model LE W E2A as made by Osram OptoSemiconductors), RAT reflector 906, 62 mm long tapered light guiding bar110 with 57 mm long emitting length, facetted light extraction film 102,57 mm×57 mm tapered light guiding plate 112, facetted light extractionfilm 114, illustrative plastic (or metal) chassis frame 908,illustrative attachment hardware 910-918, illustrative heat spreadingcircuit plate 920, and illustrative electronic circuit elements 921(with some individual examples being 922-927). This illustrative fullyconfigured light engine implementation as shown is pre-assembled forexample by bolting LED emitter 904 to illustrative heat sink element 902with two pan-head screws 910 (and 911, not labeled). Heat sink element902 may have any configuration designed for effective heat extractionfrom LED emitter 904 (effective heat extraction improves LEDperformance), including, for example, spreading over the entire topsideof the light engine much as the heat spreading circuit plate 920.

In some implementations, the RAT reflector 906, and light guiding pipe100 with attached light extracting film 102, are installed intoillustrative plastic (or metal) chassis frame 908, followed by theequivalent insertion of tapered light guiding plate 112 with itspre-attached light extraction film 114. This is followed by theattachment of illustrative heat sink element 902 with pre-attached LEDemitter 904 to the edge of illustrative plastic (or metal) chassis frameusing illustratively 4-40 screws 912 and 913. Core light generatingsub-system 900 is then attached to illustrative heat spreading circuitplate 920 using illustrative hold down hardware 914 and illustrative4-40 screw 915 as along guideline 932 plus using 4-40 screws 917-918 andpan-head screw 919. The illustrative heat spreading circuit plate may bebrought into thermal contact with heat sink element 902, mechanically orvia thermal coupling compound, in order to improve dissipation of heatfrom the LED and/or the other electronic components.

In some implementations, the illustrative heat spreading circuit platemay contain all necessary electronic and electrical interconnectionelements, collectively represented as 921, that may be needed to bringeither high voltage AC or low-voltage DC power directly to the positiveand negative terminals of LED emitter 904, via associated voltageregulation components 927, local power controlling elements 935 andillustrative electrical connection straps 936-940 required to completethe associated circuit involved. In some implementations, the localpower controlling elements 935 can be connected to the electricalinterconnection elements by a flex connector 941, for example. In thisexample, electrical components 922-931 are shown illustratively ascapacitor 922, microprocessor (integrated circuit or applicationspecific integrated circuit) 923, resistor 924 (not labeled), capacitors925-926, and voltage regulating MOSFET 927. Various combinations ofelectronics components like these (and others) may be used discretely orfunctionally integrated to perform a wide variety of effective powercontrolling functions for associated LED emitter 904, including digitalprocessing and associated response to internal or external LED emitterpower control signals.

FIG. 30A also shows symbolic representation of the light engine'sinternally interrelated light flows as described earlier in FIG. 1C. Theinput aperture of RAT reflector 906 collects substantially all outputlight 950 generated by LED-emitter 904. RAT reflector 906 is shown inthis example as a hollow reflector element placed just beyond theillustrative emitter's individual LED chips (but may be replaced byother optical elements including one or more of a lens, a group oflenses, a refractive reflector, a light pipe section, a hologram, adiffractive film, a reflective polarizer film, and a fluorescent resinwhose combination transmits substantially all light 950 into lightguiding bar 100 with desired control of the associated beam angles).

Furthermore, the LED emitter 904 (and LED emitter 1000 in FIGS. 31A-31Cand 33A-33C) may have a different form of light-emitting surface thanthat shown in the present examples (these light emitting surfaces beingthe flat exterior surface of a clear encapsulant surrounding the LEDchips). The LED emitter's light emitting surface may also be as a raisedphosphor coating, a raised clear encapsulant, a raised phosphor or clearencapsulant with micro-structured exterior surface, or a raised phosphoror a clear encapsulant with macro-structured surface. Some of theseequally applicable variations may allow for more total emitted lightand/or more effective light collection by RAT reflector 906 and/or itsoptical equivalent. Such a different light-emitting surface may also bea secondary optic coupled to the clear encapsulent around the LED chips,such as, for example, a dome lens like those commonly provided by OsramOpto Semiconductor and many other similar LED manufacturers.

In the manner shown, a substantial percentage of output light 950 fromLED emitter 904 can enter the input face of light pipe 100 as light beam952, and while inside undergoes total internal reflections within it. Ahigh percentage of light 952 is thereby turned 90 degrees bydeliberately planned interactions with micro-facetted light extractionfilm 102 as explained earlier (e.g., FIGS. 11A, 12B and 12C) and isthereby extracted uniformly from the pipe along its associated 57 mmeffective running length and ejected into air as beam 954, which in turnenters the input face of light guiding plate 112. These light flows areshown in more detail in the magnified view of FIG. 30B. Light-flow 954undergoes further total internal reflections within the light guidingplate 112 and its attached facetted light extraction film 114 and isturned 90 degrees and extracted into air evenly across the plate'ssubstantially square light distributing aperture 956 (shown more clearlyin the perspective view of FIG. 30C), thereby providing the lightengine's practical source of directional output illumination 960.

FIG. 30B is a magnified perspective view of only dotted region 892 asreferenced in FIG. 30A, providing a more detailed view of the keyelements of the engine's three-part LED light emitter sub-system(comprising illustrative 4-chip LED emitter 904, etendue-preserving RATreflector 906, and tapered light guiding pipe 100 with facetted lightextraction film 102). In this LED emitter example, there are four 1 mmsquare chips 964 arranged in a 2.1 mm×2.1 mm pattern (inside largerdielectrically-filled cavity frame 963 surrounding the chips). Other LEDchip and encapsulating dielectric combinations are as easilyaccommodated by variations on this design, including Osram's six-chipOSTAR™ versions. Positive and negative electrodes 966 and 967 areconnected to the appropriate electronic delivery members provided withinillustrative heat spreading circuit plate 920 and its illustrativeelectronic circuit elements 921, as in FIG. 30A. The commercial OSTAR™ceramic package 970 is hexagonally shaped as supplied by Osram and hasbeen trimmed to parallel surfaces 971 and 972 without electricalinterference to better comply with thinness requirements of someimplementations described herein. Mounting holes 975 are used for heatsink attachment, as shown above via low-profile pan-head mounting screws910-911 (neither shown). This illustrative RAT reflector element 906 hasthree sequential sections, each having square (or rectangular)cross-section. First section 974, placed only for this illustrationonly, slightly beyond the four OSTAR™ chips. In some implementations,this section is placed as near to the four OSTAR™ chips as mechanicallypermitted. Section 974 is etendue-preserving, in that can be designed tocollect substantially all light emitted by the group of chips at itsinput opening, with each of its four reflective sidewalls shaped asdictated by the Sine Law's input and output boundary conditions, toconvert the collected angular distribution by internal reflections ineach meridian, optimizing the entry angles to the input face (not shown)of tapered light guiding pipe 100. Second section 976 and third section978 surround the illustrative 3 mm×3 mm entrance face of light guidingpipe 100 as one way of facilitating mechanical mounting and alignment.Neither section 976 or 978 has any optical function or special shape,and may be eliminated.

In some implementations, tapered light guiding pipe 100 is injectionmolded. All mold tool surfaces in this case are provided a featurelesspolished mirror finish. Molding materials are of optical grade, forexample, optical grade PMMA (i.e., polymethyl methacrylate) or highestavailable optical grade polycarbonate obtainable to reduce itsintrinsically higher bulk absorption loss. In addition, the corners andedges of light guiding pipe 100 can be made as sharply as possible tominimize scattering loss from of by roughened edges, to minimizeunwanted TIR failure, and to maximize the edge-to-edge optical couplingwith the facetted light extraction film 114. Facetted light extractionfilm 114 is attached, as described earlier, to the back surface of pipe100 by means of a thin clear optical coupling medium 320 as in FIG. 11A(e.g., pressure sensitive adhesive). In these implementations, the lightextracting facets 322 are made of either PMMA or polycarbonate (e.g., byembossing, casting, or molding) and then coated with high reflectivityenhanced silver (or aluminum) 340.

FIG. 30C provides a perspective view of the completely assembled form ofthe fully-configured light engine implementation shown in explodeddetail 890 in FIG. 30A, as described in U.S. Provisional PatentApplication Ser. No. 61/104,606, which is hereby incorporated byreference in its entirety. Total engine thickness is determinedprimarily by the thickness of illustrative heat sink element 902 and anyadditional net thickness associated with the attachment of illustrativeheat spreading circuit plate 920. The collimated down light illuminationthat develops projects evenly from substantially the entire square (orrectangular) output aperture area 934.

FIG. 30D illustrates a related geometric form in which metal coatedfacetted layer 102 may be replaced by plane reflector 274 (as in FIG.8A) and a separate facetted light extraction element 103, similar to 104but having uncoated facets of an appropriately different geometricaldesign placed just beyond the front face of pipe 100 (facet verticesfacing towards the pipe surface). Light flow 952 internal to pipe 100,in either form, induces sequential leakages from the pipe itself that oninteraction with the facets 322 (see FIG. 11A-11C) of facetted lightextracting film used cause sequentially distributed output light 954 ina direction generally perpendicular to the front face of pipe 100.

FIG. 30E is a perspective view showing the variation of FIG. 30D appliedto light guiding plate 112. In this implementation, a reflective layer980 (similar to 274) is placed on (or slightly separated from) thetopside surface of light guiding plate 112, and a separate facettedlight extraction sheet 982 (similar to 103) is placed just beyond theplate's opposing side light output surface. This illustration isprovided to show a variation of the alternative light guiding,extracting and collimating form as illustrated in FIG. 30D applied to alight guiding plate 112 rather than to a light guiding pipe 100. Edgeemitted output light beams 954 from the illustrative collimating lightbar system example composed of light guiding pipe 100 and lightextraction film 103 (or, as another example, from the collimating lightbar system illustrated previously in 30B composed of light guiding pipe100 and light extraction film 114) enter the input edge of light guidingplate 112 and as a result of passage through the plate system, areextracted across nearly the entire output aperture as collimated outputbeam 960.

In this implementation, collimated light (not shown) extracts obliquelyfrom tapered plate 112 and mirror 980 into the thin air region belowplate 980 and above facetted film 982 (as was shown previously in FIGS.7A-7C), and then redirected or turned as output down light (output beam960) by passage through facetted film 982, which may serve as alight-turning film.

Another practical form as illustrated in FIG. 30D arises when facettedfilm 982 is removed. This results in a beam of light emanating from thefull surface of plate 112 having the obliquely-angled pointing directionshown in FIG. 7C, a useful behavior that will be described furtherbelow.

The implementation illustrated in FIGS. 30A-30D (as in FIGS. 1A-1D,3A-3E, 4, 16A-16B, 26, and 28) employs a tapered light guiding pipe 100to collimate LED input light in one meridian while presenting that lightas input across the edge of a tapered light guiding plate deployed topreserve the collimation of the light received, while collimating thatsame light in its orthogonal meridian, so as to produce completelycollimated output illumination.

Another implementation was introduced in FIGS. 2A-2E, replacing thetapered light guiding pipe 100 and its associated elements with areflector-based alternative. A linear array of one or more etenduepreserving RAT reflectors was arranged to collimate LED input light inone meridian while presenting that light as input across the edge of atapered light guiding plate 112 arranged to preserve the reflector-basedcollimation of the light received, while collimating that same light inits orthogonal meridian, so as to produce completely collimated outputillumination.

FIGS. 31A-31D illustrate a practical implementation of this form of thisdisclosure.

FIG. 31A provides an exploded top perspective view of a practical singleemitter segment 998 (following the general example of FIG. 2A) for afully configured multi-emitter light engine implementation based on thisetendue-preserving RAT reflector-based means of providing partiallycollimated light input to a light guiding plate. This implementationexample illustrates use of a six-chip LED emitter 1000 manufactured byOsram Opto Semiconductor, e.g., Model LE CW E3A, mounted on the samehexagonal substrate as shown above, and trimmed to rectangular shape ina manner also shown above. LED emitter 1000 in this an ensuing examplesmay have a different form of light emitting surface than that shown aswas discussed above. Such a different light-emitting surface may be asecondary optic coupled to the clear encapsulent around the LED chips,such as, for example, a dome lens like those commonly provided by OSRAMand many other LED manufacturers. Other variations, too numerous toillustrate, only compliment practice.

In this illustration, LED emitter 1000 is attached to illustrative heatsink element 1002 using two pan-head screws 910 and 911 as was shown inFIG. 30A. The form of heat sink 1002 indicates one possible arrangementof heat extraction fins 1003 for efficient heat removal by ambient airpassing between them. Heat sink 1002 may have any configuration designedfor effective heat extraction from LED emitter 1000 (effective heatextraction improves LED performance), including, for example, spreadingover the entire topside of the light engine and/or along its sides.Wide-angle light emission from the 6 chips of LED emitter 1000 iscollected by the similarly sized input aperture of etendue-preservingRAT reflector 1004. RAT reflector 1004 is constructed for this examplein four principal parts, two identical side elements 1006 and 1008,whose highly polished sidewall mirrors 1010 and 1012 form two opposingsides of the associated reflector's four-sided rectangularcross-section, and two identical top and bottom elements 1014 and 1016whose highly-polished reflecting surfaces 1018 and 1020 complete thefour-sided reflector's rectangular cross-section. The four constituentparts of RAT reflector 1004 may be attached by adhesive, may be weldedor soldered together, and as illustrated, may be bolted together usingrecessed screws 1022-1025 which pass through through-holes made in toppart 1016 and are received by correspondingly tapped holes in bottompart 1014. Four higher precision dowel pins 1028-1031 (within only 1028labeled) may be used for additional accuracy in reflector alignment.Then, one way of assuring proper alignment between the rectangularoutput aperture of RAT reflector 1004 and the input edge of taperedlight guiding plate 1034 is illustrated in this example by addingreflector overhang portions 1036 and 1038, reflective gripping plates1040 and 1042, and set screws 1044 and 1046 which apply sufficientholding pressure to gripping plate 1042 (and thereby to light guidingplate 1034) via tapped holes 1048 and 1050.

In the illustration of FIG. 31A, light guiding plate 1034 is similar toplate 112, but in this case is made narrower in width than in length tomatch the output aperture size of RAT reflector 1004, enabling efficientlight power transfer from RAT reflector to light guiding plate andfurther enabling uniform plate light extraction (compared to, say, amuch wider plate which would have dark bands outside the cone of lightemitted by the RAT in XY meridian). The example of FIG. 31A showsfacetted light extraction film 1035 (similar in design to 114) affixedin the manner described to the topside of light guiding plate 1034.Alternately, as shown in the optional extracting form of FIG. 30D,facetted film 1035 may be replaced by a plane mirror, and anotherfacetted film similar to 982 may be placed instead just below outputplane 1052 of light guiding plate 1034. It is understood that lightextraction film 1035 may be considered a light turning film, as thelight may actually be extracted from the tapered light guiding plate1034 due to the tapered shape of the light guide and the relationship ofthe indices of refraction of the light guide and any surroundingmaterial.

FIG. 31B is a perspective view of the assembled version of the practicallight engine example shown exploded in FIG. 31A. Illustrative RATreflector 1004 assembles along dotted lines 1054 and 1056. Heat sink1002 with attached LED emitter 1000 bolts to RAT reflector 1004 using,for example, two diagonally deployed attachment screws 1058 (shown) and1060 (hidden). When positive and negative DC supply voltage is appliedto positive and negative terminal wires 1062 of LED emitter 1000, lightflows as has been explained from LED emitter 1000 through RAT reflector1004, into and through light guiding plate 1034, and becomes doublycollimated output beam 1064 (similar to doubly collimated far-fieldillumination 10 as shown in FIG. 2A) with angular extent in theZX-meridian, +/−θ_(X), being set by the collimating characteristics oftapered light guiding plate 1034 (and any ancillary characteristicsimparted by facetted light extraction film 1035), and with angularextent in the ZY-meridian, +/−θ_(Y), being set by the collimatingcharacteristics of etendue-preserving RAT reflector 1004 established byits output aperture in the XY plane.

In the present example, RAT reflector 1004 is matched to dimensions ofthe six-chip Osram OSTAR™ Model LE CW E3A with an input aperture that isapproximately 2.2 mm along Z-axis 6 and 3.6 mm along Y-axis 5. It is the3.6 mm input aperture dimension that drives the RAT reflector's outputaperture width that is further matched to width 1068 of light guidingplate 1034 being used to achieve an angular extent 71 that can bedesired.

FIG. 31C is a schematic top view providing a clearer description of theunderlying geometrical relationships that are involved in matching LEDemitter 1000, RAT reflector 1004 and light guiding plate 1034. FIG. 31Cis schematic a top cross-sectional view of the angle transformingreflector arrangement shown in FIGS. 31A-31B along with LED emitter1000. In this illustration, the reflector's top element 1016 (and itsillustrative attachment screws 1022-1025) are removed to reveal theunderlying geometrical relationships controlled by equations 10 and 11(in terms of the reflector element's input aperture width 1070, d₁, itsideal output aperture width D₁, its ideal length L₁, and its idealoutput angular extent +/−θ₁), with +/−θ₀ being the effective angularextent of the group of LED six chips 1071 in illustrative LED emitter1000 (effectively +/−90 degrees). Similar relationships, equations 12and 13, govern the orthogonal meridian's ideal geometry d₂, D₂, L₂, andθ₂, but are not illustrated graphically. In this case, interchangeably,θ₁ represents θ_(X) and θ₂ represents θ_(Y). The symmetrically disposedreflector curves 1072 and 1073 of reflector section 1074 as shown inFIG. 31C are ideal in that their curvatures satisfy the boundaryconditions given by equations 10 and 11 at every point. Section 1074only shows the initial length 1076, L₁₁, of an otherwise ideal reflectorlength L₁. Initial length L₁, is expressed as f L₁, where f is afractional design value typically greater than 0.5 (e.g., f=0.62 in thepresent illustrative example).d ₁ Sin θ₀ =D ₁ Sin θ₁  (10)L ₁=0.5(d ₁ +D ₁)/Tan θ₁  (11)d ₂ Sin θ₀ =D ₂ Sin θ₂  (12)L ₂=0.5(d ₂ +D ₂)/Tan θ₂  (13)

θ₀ represents the width of the beam, here the beam being emitted by theLED light emitter, measured from the normal. For an LED, it isreasonable to assume a Lambertian distribution and hence it is usually areasonable approximation in practice that θ₀ can be assumed to be about90 degrees, especially with the LED light emitters used in accordancewith some implementations of this disclosure. The ideal reflectorlengths L1 and L2 can be expressed more compactly, in this case, as inequations 14 and 15.L ₁=0.5d ₁(Sin θ₁+1)/(Sin θ₁ Tan θ₁)  (14)L ₂=0.5d ₂(Sin θ₂+1)/(Sin θ₂ Tan θ₂)  (15)

A unique design attribute of this particular reflector fed light engineexample is that the angular extents of the output illumination 1064 ineach output meridian (+/−θ₁ and +/−θ₂) are completely independent ofeach other. The reflector geometry developed in FIG. 31C (i.e., meridian1) determines the engine's output angular extent (+/−θ₁ or +/−θ₁₁) inonly that one meridian. The engine's output angular extent in the othermeridian (+/−θ₂) is determined substantially by the (independent)behavior of the tapered light guide plate 1034 and associated facettedfilm sheet 1035).

Matched to the illustrative six-chip Osram LED emitter 1000, d₁=3.6 mm,as set by the size, spacing and surrounding cavity of Osram's threeinline 1 mm LED chips, +/−θ₁=+/−10.5 degrees by design choice, so D₁(from equation 10) becomes in this case approximately 3.6/Sin(10.5)=19.75 mm, and the ideal reflector length L₁ associated with theseconditions becomes (from equation 11) 0.5 (3.6+19.75)/Tan(10.5)=63.0 mm.The choice of 10.5 degrees is only illustrative. There are many otherpractical design angles to choose from, most efficiently those widerthan 10.5 degrees.

Optical ray trace simulations (using the commercial ray tracing softwareproduct ASAP™ Advanced System Analysis Program, versions 2006 and 2008,produced by Breault Research Organization of Tucson, Ariz.) have shownthat ideal reflectors of this type (governed the Sine Law equations10-13) can be trimmed back in length from their ideal, L₁, withoutincurring a significant penalty in their effective angle transformingefficiency (or output beam quality). As noted above, the lightdistributing engine arrangements disclosed herein can deploy anglespreading output aperture films (e.g., the parabolic lenticular lenssheets shown FIGS. 24A-24G and 25). Further, the tolerance to suchdeviations in design from ideal dimensions becomes less critical whenused in the present light distributing engine arrangement. Accordingly,in the present example, the etendue-preserving RAT reflector unit (1004)has been reduced in length by 38%, to a total length, L₁₁ (as shown inFIG. 31C), of 39 mm. As a result, illustrative LED input ray 1080 isreflected from reflector curve 1073 at point 1082 and strikessymmetrically disposed reflector curve 1072 at point 1084, reflectingideally outwards without an additional reflection as output ray 1086 ofLED light emitter 1000, making the intended output angle θ₁ (1088) withreflector axis line 1090.

The small deviation from ideality tolerated with the reflector lengthreduction as shown in the example of FIG. 31C is indicated by thetrajectory differences between LED input ray segments 1092 and 1094(dotted). The trajectory of ray 1092 (angle θ₁ with axis line 1088) isdetermined by the ideal (etendue preserving) reflector length L₁ and theideal output aperture width D₁, such that by geometry, Tan θ₁=(D₁/2)/L₁,set by choice to 10.5 degrees in the present example. The devianttrajectory of ray 1094, however, is set by the reduced length 1074, L₁₁,and the proportionally reduced output aperture width 1096, D₁₁, as Tanθ₁₁=(D₁₁/2)/L₁₁. In this example, L₁₁=39 mm and D₁₁=18.75 mm, soθ₁₁=13.5 degrees, which is only a small degree of angular deviation, andinconsequential to most commercial lighting applications. Furthermore,it is only a fraction of the total rays that fall into this deviation,whereas a significant fraction remain within the ideal output range+/.+−.θ₁.

Whenever more sharply cut-off angular illumination is required usingthis form of thin-profile reflector fed light engine (as in FIGS. 2A-2E,and 31A-31B), a lesser degree of reflector truncation may be employed.

The RAT reflector's design in the orthogonal meridian (+/−θ₂) is made todeliberately pre-condition light for optimum coupling efficiency to thecorresponding entrance face of light guide plate 1034 and its associatedfacetted light extraction film 1035). Example angular conditions forthis purpose as described earlier (e.g., FIGS. 3D-3E, and 5A-5C), are+/−50 degrees and +/−55 degrees (in air) for a 3 mm thick tapered lightguiding plate 112 having a 3-degree taper-angle made of highest opticalgrade transparent plastic or glass.

FIG. 32A shows a simplified example of a multi-emitter implementation,following its general introduction in FIGS. 2A-2E, and in FIGS. 31A-31Cabove. Practical packaging details related to heat sinks, the LEDemitter's electrical interconnection substrate, and the means with whicheach light engine segment is attached to adjacent segments and to theassociated light guiding plate 1034 is omitted in this example forvisual clarity. This particular example deploys seven parallel inputemitting channels, shown co-joined to one another to form a single inputsource 1098 to the same type of tapered light guiding plate 112 or 1034illustrated earlier in FIGS. 3A-3B, 4, 26 and 28. The top reflectorsheet that covers the seven individual input reflector elements has alsobeen left out for visual simplicity. For this example, the operative RATreflector is matched for use with the four-chip Osram OSTAR™ model LE WE2A as was used in the example of FIG. 30A. The corresponding inputaperture 1070 in FIG. 31C is 2.2 mm. Only the four-chip frame portion964 (as referenced earlier in FIGS. 30B and 30D) of LED emitter 904 isshown in the present illustration for additional visual clarity. If theassociated RAT reflector's design angle, θ₁ as in FIG. 31C, is made awider one for this example at +/−15 degrees, the corresponding outputaperture size, D_(I), without the reflector length truncation applied inFIG. 31C, becomes by means of equation 10, (2.2)/Sin(15) or 8.5 mm(along the plate system's input edge, also the system's Y axis 5). Theorthogonal pair of reflector sidewalls (1014 and 1016 as in the exampleof FIG. 31C) convert the +/−90-degree input light from the four-chip LEDemitter being used to the narrower angular range in the system's XZmeridian (e.g., +/−52.6 degrees). When seven such emitter-reflectorcombinations are placed adjacent (or nearly adjacent) to each other asillustrated in FIG. 32A, the collective length they occupy along thesystems Y-axis 5 is a minimum of 59.5 mm. Matching efficiently to thiswidth requires using a light guiding plate 1034 whose width along thesystem's Y-axis 5 is at least 59.5 mm.

For those lighting applications requiring higher lumen levels, thissegmented array-type input engine 1098 can be especially useful. The7-emitter example shown is about as thin as earlier single emitterimplementations shown. One advantage of this form is that with sevenseparate LED emitters the collective engine is able to supply up toseven times the net lumens supplied by each LED emitter that is beingused. If the total emitted lumen output of the four-chip LED emitter isfor example taken as 400 lumens, the net throughput efficiency of eachRAT reflector segment, 93%, and the net throughput efficiency of taperedlight-guiding plate 1034, 86%, then the total lumen far-field output forthe thin illumination system 1 becomes (7)(400)(0.93)(0.86) or 2,240lumens.

Another advantage of the multiple-emitter system is that the same lumensas a 1-emitter system can be achieved at lower operating current, whichresults in higher power efficiency (lumens/Watt) operation because LED'sgenerally operate more efficiently at lower currents. This can alsoimprove the system's lifetime, as the LED's will degrade more slowlywhen operated at lower currents. Furthermore, in a multiple emittersystem, some LED's can be left entirely off for some period (as long asuniform emission across the entire plate is not required), therebysaving them for future use, which can further increase the lifetime ofthe whole system. As one simple example, by using a 7-emitter system ina lighting application where one LED can produce sufficient lumens forthe application, the other six LED's can be left off and usedsequentially as each LED fails, effectively increasing the lifetime ofthe system by 700%. Performance consistency can be achieved by turningon one LED gradually as another gradually fails.

Yet a further advantage of a multiple-emitter system is that a wideroverall range of dimming levels. Also, a wider overall range of colorand color mixing options are possible through use of different colorLED's.

FIG. 32B illustrates a perspective view of the system in FIG. 30A, withtop reflector 1108 added, and also includes an example of the system'srealistically computer-simulated output beam profile for the designparameters involved. The far field output 1110 developed by this higheroutput implementation has a net far-field angular distribution that is+/−15 degrees by +/−5 degrees with the same rectangular field patterncharacteristics as seen for the earlier illumination systemimplementations.

Numerous implementations may be developed as various groupings of thebasic single-emitter engine segment shown first generally in FIG. 2A,and then as more detailed segment 1037 in FIG. 31B. A few illustrativeimplementations of engine groupings are shown in FIGS. 33A-33C.

FIG. 33A shows a topside perspective view of two side-by-sidedown-lighting engine segments 1037 of emitter-reflector-light guidingplate thin illumination system invention variation as illustrated inFIG. 31B.

Frame 1120 is added as a secure packaging for light guiding plate 1034and its associated light extraction film 1034, as well as any lightshaping films not shown. The uniformity of far-field illumination isunaffected by the framing of the light guiding plate apertures. In thepresent example, the framing width 1122 is arbitrarily made 3 mm, butcould be more or less as desired. The clear illuminating apertures inthis illustration are about 57 mm×18.75 mm. Illustrative heat sinkelements 1002 each extend 24.35 mm beyond each LED emitter 1000 attachedto them but in other configurations could extend longer and/or run overthe top of the engine and/or its sides. The total length of this engineexample, end-to-end, is about 128 mm, and the total two-engine outsidewidth is 49.54 mm. Maximum thickness, 15 mm in this example, is limitedby the mechanical-design of the Osram OSTAR™ ceramic substrates used(which were sliced down to 15 mm as shown).

Actual prototype engines have been made to this exact design, and theirmeasured laboratory performance agrees closely with performancepredictions of throughput efficiency and far-field beam profiles made bycomputer simulation using the salient parameters described above.

FIG. 33B shows a topside perspective view of two in-line down-lightingtwo-engine segments of the emitter-reflector-light guiding plate thinillumination system invention variation as illustrated in FIG. 31B.

FIG. 33C shows a topside perspective view of two counter-posedtwo-engine segments 1037 of the emitter-reflector-light guiding platethin illumination system invention variation as illustrated in FIG. 31B.

Many other combinations and variations are equally possible. Thecombination of multiple engines (whether of the engine types shown inFIGS. 31-33, or the engine types shown previously or subsequently) alsoallows variety of functions within a single system, such as variety inpointing direction and angular extent. For example, one of the enginescould point light toward a wall while another points light downwards. Asanother example, one engine could project light in a +/−5 degree squarecone, while another projects light in +/−20 degree circular cone. Manymulti-functional combinations and variations have been and could beimagined. Some have been described in a related U.S. Provisional PatentApplication Ser. No. 61/104,606.

Light guiding plates 112 and 1034 used in all examples of the presentthin illumination system invention herein share a tapered cross-sectionthat's been extruded linearly along one Cartesian axis (e.g., Y-axis 5).The associated facetted light extraction films, whether attached to oneside of the light guiding plate's tapered cross-section, as shown inFIG. 11A, or as a separate facetted element, separated slightly from thelight guiding plate's tapered cross-section, as shown in the perspectiveview of FIG. 30D, are extruded linearly along the same Cartesian axis(e.g., Y-axis 5). The result in both cases is a constant cross-sectionalong the axis of extrusion.

FIG. 34A is a schematic perspective illustrating execution of the globalboundary condition for linear extrusion of the tapered light guidingplate (112 and 1034), wherein the normal to prototype taperedcross-section 1128, vector 1130, follows a straight axial extruding line1132, illustratively parallel to the system's Y-axis 5. Such linearlyextruded plates are used in the examples of FIGS. 3A-3B, 5A, 7A-7C,8A-8D, 9, 11A, 12B-12E, 13A-13C, 16B, 26, 28, 30A, 30E, 31A-31B,32A-32B, and 33A-33C. Cross-sectional shape and dimensions are heldconstant, as illustrated by the reference cross-sections 1134-1140.Extruded boundary surface 1142 becomes the light input plane or face ofthe extruded light guiding plate. Line 1144 is the tapered light guideplate's mathematically idealized knife-edge or peripheral edge. Inpractical production, the actual knife-edge is an approximation, as wasshown in FIG. 5A.

FIG. 34B shows in schematic perspective that the linear boundarycondition of FIG. 34A also forms the linearly extruded facetted lightextraction films as were shown in FIGS. 3A-3B, 4, 26, 28, 30A, 30D, 31A,31D, 32A-32B, and 33A-33C. Prototype facet cross-section 1146 followsthe same direction vector 1130 for its extrusion along straight axialextruding line 1132 as is shown in FIG. 34A for the linearly extrudedtapered light guiding plate.

Not all useful light guiding plates and facetted light extraction films(and means to couple the plates and films together) are extrudedlinearly. Radially extruded light guiding plates and radially facettedlight extraction films enable circular, as well as square andrectangular forms of thin illumination systems, for example. In someimplementations, irregularly shaped light guides or light guiding platescan be extruded radially. In these radially extruded forms, input lightfrom one or more light sources, for example, one or more LED emitters,is applied to a light entry surface which can be disposed, for example,near a center portion of the light guide, as discussed below. In someimplementations, the light entry surface can be formed by a recess ordepression in the top and/or bottom surfaces of the light guide. Forexample, the light entry surface can be formed by a cylindrical recessthat extends partially, or completely, through the light guide. In someimplementations, a light guide can include more than one light entrysurface such that light can be injected radially into the light guide bydifferent light sources that are spaced apart from one another. In thisway, light may be injected radially from one or more light sources viathe light entry surface.

FIG. 34C illustrates in schematic perspective a basic execution of theradially constrained extrusion to form disk-type tapered light guidingplates. Prototype tapered cross-section 1128 is extruded about an axisline 1148 (running parallel to system Z-axis 6) such that thecross-section's prevailing direction vector 1150 follows circular guidepath 1152. As this constant cross-section light guiding solid plate isdeveloped, a cylindrical bounding surface 1154 is formed in the center,and a mathematically idealized circular knife-edge or peripheral edge1156 is formed at the periphery. In some implementations, the guidingplate can be tapered such that the light illumination surface and theupper or top surface of the guiding plate define an angle α therebetweenat the peripheral edge of the guiding plate. In some implementations,the angle α can be greater than 1 degree and less than 15 degrees, forexample, between about 2 degrees and about 8 degrees (including 2degrees, 3 degrees, 4 degrees, 5 degrees, 6 degrees, 7 degrees, 8degrees, or any value between any two of these values). In this way, amaximum longitudinal dimension of the light guiding plate or light guidecan be relatively thin, for example, below 50 mm or 2 inches. However,depending upon the taper angle α and the maximum radial dimension, lightguiding plates with longitudinal dimensions between about 1 mm and about16 mm, for example, between about 2 mm and 6 mm, can be made.

FIG. 34D shows in schematic perspective the circular taperedcross-section light guiding plate 1160 that results from executing theradial extrusion illustrated in FIG. 34C.

FIG. 34E is a schematic perspective view illustrating the correspondingradial extrusion process for facetted cross-section 1162 andcross-section normal 1164 sweeping about axis line 1148 and circularguide path 1152 to form radially facetted light extraction film 1166.Central hole 1168 can form a light entry surface to facilitate theincorporation of an LED emitter, or other light source, and acorresponding light reflector or optical coupling which can bederivative of the etendue-preserving RAT reflectors (or functionallyequivalent optic) described above, in some implementations.

FIG. 34F is a topside schematic perspective view illustrating the radiallight extracting film 1166 that results from executing the radialextrusion illustrated in FIG. 34E. Central hole 1168 facilitatesincorporation of an LED emitter and a corresponding light reflectorderivative of the etendue-preserving RAT reflectors described above.

FIG. 35A is a cross-sectional perspective view illustrating radiallyfacetted light extracting film 1166 of FIG. 34E and circular lightguiding plate or light guide 1160 of FIG. 34D combined in accordancewith one additional form of this disclosure. Light entering cylindricalboundary surface 1154 flows radially through the body of plate 1160,interacts with radially facetted light extraction film 1166 in eachcross-section just as it did in the equivalent cross-section of FIGS.11A-11C, and is output from the circular plate's unobstructed surface1157 along system's Z-axis 6, as equally well-collimated illumination.Layer 1172 is the functional equivalent of optical coupling adhesive 118as shown for example in FIG. 3B or 320 as shown in FIGS. 11C-11D. Inthis example of this disclosure, the faceted light extraction film 1166has been attached for convenience to the plane (or flat) side of thetapered light guiding plate 1160. It may be attached to either sidewithout performance penalties. As discussed below, in someimplementations, a light guide can reflect light from a reflective orupper surface through an illumination or output lower surface without aradially facetted light extraction film.

FIG. 35B is a cross-sectional perspective view illustrating the internaldetails of one example of a practical combination of illustrative LEDemitter 1000 (as in FIG. 31A) with radial light guiding system 1170 ofFIG. 35A. The linear light guiding system implementation of FIGS.31A-31B used etendue-preserving RAT reflector 1004 as its means of lightcoupling from LED emitter 1000 to linear light guiding plate 1034. Theone sided radially symmetric equivalent of linearly emitting RATreflector 1004 is radially symmetric (angle transforming) reflector1174. The packaging of Osram's six-chip OSTAR™ model LE CW E3Anecessitates using a one sided reflector. Sidewall curvature 1178 ofreflector 1174, like that of RAT reflector 1004, is driven by theboundary conditions of etendue-preserving equations 10-15, and isthereby related to the linearly extruded sidewall shape of RAT reflector1004, as in FIG. 31C. The shape of reflector 1174 is meant to beillustrative of its general form and may be implemented in a variety ofmetal, metal-coated dielectric and total internally reflectivedielectric formats. Similarly, the plane cylindrical input face 1154 oftapered light-guiding plate 1034 is also only one example. It may becurved or facetted in some situations, and the taper plane may also bevaried in shape nearest input face 1154 as a result. As discussed below,in some implementations, the reflector 1174 can be configured tocollimate light radially toward a periphery of the light guidereflective surface of the light guide or a facetted light extractionfilm. Such collimated light may be further collimated by the taperedradial shape of the light guide reflective surface of the light guide orthe facetted light extraction film to provide for an output that iscollimated in two orthogonal Cartesian medians through the output orillumination surface 1157.

FIG. 35C is a magnified view 1180 of cross-section of FIG. 35B showingfiner details of the light input region of this illustrative radial formof the thin emitter-reflector-light guiding plate illumination system.The process of light transmission and light extraction was explainedearlier (e.g., FIGS. 11A-11C and 12B) and applies without modification,to the radial form, as each radial cross-section remains that of FIG.11A. For convenience, a few illustrative rays 1181-1187 are shown in thecross-sectional plane. With DC operating voltage applied to terminals1062 of LED emitter 1000, ray 1181 is emitted outwards from one of theemitter's six LED chips. This illustrative ray strikes the reflectingsidewall curvature 1178 of radial angle transforming reflector 1174, andas did RAT reflector 1004, redirects ray 1181 as ray 1182 towardscylindrical entrance face 1154 of the light guiding plate 1160. Asdescribed below, in some implementations the radial transformingreflector 1174 may be replaced by other functionally similar couplingoptics, including one or more of circularly symmetric reflectors ofdifferent surface curvature than 1178, one or more circularly symmetricreflectors of with segmented surfaces, a lens, a group of lenses, arefractive reflector, a light pipe section, a hologram, a diffractivefilm, a reflective polarizer film, and a fluorescent resin. Furthermore,the LED emitter 1000 may have a different form of light-emitting surfacethan that shown (the light emitting surface shown being the flatexterior surface of a clear encapsulent surrounding the LED chips), suchas a raised phosphor, raised clear encapsulent, raised phosphor or clearencapsulent with micro-structured exterior surface, or raised phosphoror clear encapsulent with macro-structured surface, said different formallowing more total emitted light and/or more effective light collectionby reflector 1174 or its coupling optic equivalent. Such a differentlight-emitting surface may also be a secondary optic coupled to theclear encapsulent around the LED chips, such as, for example, a domelens like those commonly provided by OSRAM and many other LEDmanufacturers (as mentioned above).

On entry, illustrative ray 1182 becomes propagating ray 1183 and thenpropagating ray 1184 which with similarity to ray path 330-332-334-336in FIG. 11A, generates extracted output ray 1185 (which escapes taperedlight-guiding plate 1160 into air at point 1190 on the plate's outersurface 1157. Remaining light energy continues to propagate withintapered light guiding plate 1060 by total internal reflection asillustrative ray segments 1186 and 1187.

FIG. 35D shows a cross-sectional view of an example lighting device orillumination device 2000 including a tapered light guide or guidingplate 2101. To assist in the description of the implementationsdescribed herein, the following coordinate terms can be used, consistentwith the coordinate axes illustrated in FIG. 35D. A “longitudinal axis”extends generally orthogonally to the light guide 2101 of theillumination device 2000 (similar to the Z axis of FIG. 1A). A “radialaxis” is any axis that is normal to the longitudinal axis, for example,any axis that extends in the XY plane of FIG. 1A. In addition, as usedherein, “the longitudinal direction” refers to a direction substantiallyparallel to the longitudinal axis and “the radial direction” refers to adirection substantially parallel to a radial axis.

As shown, the light guide 2101 can be radially tapered from a centerportion to a peripheral edge 2109 defined by the joinder of an uppersurface 2103 and a lower surface 2105. In other words, where the uppersurface 2103 and the lower surface 2105 terminate at their closestproximity, or where they meet. As discussed below, a reflective surfacecan be disposed adjacent to the upper surface 2103 so as to reflectlight propagating within the light guide 2101 towards the lower surface2105. In some implementations, the upper surface 2105 can include areflective surface. For example, at least a portion of the upper surface2105 can be reflective so as to turn or reflect light propagating withinthe light guide 2101 away from the upper surface 2104. The lower surface2105 can be referred to as an illumination or output surface based onthe light that exits the light guide 2101 through this surface. Ofcourse, the terms upper and lower with respect to the upper surface 2103and lower surface 2105 are used relative to the schematic depiction ofthe illumination device 2000 in the figures and a person having ordinaryskill in the art will readily appreciate that, in some implementations,the upper surface of a light guide can be an illumination surface and/orthat the lower surface of a light guide can be a reflective surfaceand/or be disposed adjacent to a reflective surface, for example.

Still referring to FIG. 35D, an angle α can be defined between the uppersurface 2103 and the lower surface 2105. Because the upper surface 2103and the lower surface 2105 meet at the peripheral edge 2109, the angle αcan define the taper of the light guide 2101. Thus, in someimplementations the angle α can be referred to as the taper angle of thelight guide. In some implementations, the angle α can be less than 15degrees, for example, greater than 1 degrees and less than 15 degrees.For example, the angle α can be between about 2 degrees and about 8degrees. In some implementations, the angle α can be greater than 15degrees, for example, about 30 degrees.

As shown, the light guide 2100 has a maximum radial dimension D definedbetween opposing sides of the peripheral edge 2109. The light guide 2100also has a maximum thickness or longitudinal dimension T. In someimplementations, the maximum radial dimension D can be selected suchthat the illumination device 2000 and light guide 2101 fit within arecess for a given lighting fixture, for example, a recess for a fixtureconfigured to receive a PAR lighting device. For example, the dimensionD can be less than 8 inches such that the light guide 2101 may fitwithin a PAR64 fixture, the dimension D can be less than 7 inches suchthat the light guide 2101 may fit within a PAR56 fixture, the dimensionD can be less than 5.75 inches such that the light guide 2101 may fitwithin a PAR46 fixture, the dimension D can be less than 4.75 inchessuch that the light guide 2101 may fit within a PAR38 fixture, thedimension D can be less than 4.5 inches such that the light guide 2101may fit within a PAR36 fixture, the dimension D can be less than 3.75inches such that the light guide 2101 may fit within a PAR30 fixture,the dimension D can be less than 2.5 inches such that the light guide2101 may fit within a PAR20 fixture, and/or the dimension D can be lessthan 2 inches such that the light guide 2101 may fit within a PAR16fixture. Of course, in some implementations, the light guide 2101 andillumination device 2000 can be configured to fit within the recesses ofother standard fixtures. In this way, the illumination device 2000 maybe used with existing lighting fixtures without requiring a retrofit orconversion for the use of the illumination device 2000.

As described above, in some implementations a light guide or lightguiding plate may be relatively thin thereby limiting the weight andfootprint of a lighting device. Because the angle α of the light guide2101 can be less than 15 degrees, the maximum longitudinal dimension Tof the light guide 2101 can be limited by the angle α and the maximumradial dimension D. In some implementations, the light guide 2101 canhave a maximum longitudinal dimension T that is between 1 mm and 16 mm.For example, the light guide 2101 can have a maximum longitudinaldimension T that is between 2 mm and 6 mm.

With continued reference to FIG. 35D, in some implementations the lightguide 2101 can include a light entry surface 2107 disposed near thecenter of the light guide 2101. In this way, light may be injected intothe light guide 2101 through the light entry surface 2107 and theinjected light may propagate radially toward the peripheral edge 2109.In some implementations, the light entry surface 2107 can be formed by arecess or depression, for example, a columnar recess, that extends atleast partially through the light guide 2101 in the longitudinaldirection. As shown, the light entry surface 2107 can be formed by acolumnar recess that extends between the upper surface 2103 and thelower surface 2105. Such a recess may be formed by etching as describedbelow with reference to the example method of FIG. 54.

In some implementations, the illumination device 2000 can include one ormore light sources 2203 disposed within the light guide 2101. The one ormore light sources 2203 can include an LED source or LED emitter similarto those described above. For example, the one or more light sources2203 can be electrically and/or mechanically coupled to a circuit plate2201 that may be utilized to bring either high voltage AC or low-voltageDC power directly to the one or more light sources 2203 via voltageregulation components, local power controlling elements, and/orillustrative electrical connection straps. Various combinations ofelectronic components may be used discretely or functionally integratedto perform a wide variety of effective power controlling functions forthe one or more light sources 2203, including digital processing andassociated response to internal or external power control signals.

As shown, the one or more light sources 2203 can be configured to emitlight in an upward or longitudinal direction toward the upper surface2103 of the light guide 2101 (for example, away from the lower surface2105). In some implementations, the illumination device 2000 canoptionally include an optical coupler 2301 disposed within the lightguide 2101 in an optical path between the one or more light sources 2203and the light entry surface 2107. In this way, the optical coupler 2301can be configured to couple light emitted from the one or more lightsources 2203 into the light guide 2101 through the light entry surface2107. For example, the optical coupler 2301 can include one or morecurved reflective surfaces configured to redirect light travelling inthe longitudinal direction that is received from the one or more lightsources 2203 toward the light guide 2101 in the radial direction. Insome implementations, the optical coupler 2301 can be configured tocollimate light, that is to reduce the angular divergence of a beam oflight, in the radial direction and the collimated light may be injectedinto the light guide 2101 via the light entry surface 2107. In someimplementations, the optical coupler 2301 can reflect light via TIR,metallic reflection, and/or dielectric reflection. The optical coupler2301 may be an etendue-preserving reflector similar to reflector 1174 ofFIG. 35B, for example. The optical coupler 2301 can include one or moregrating or lens based structures to couple light emitted from the one ormore light sources 2203 into the light guide 2101.

In some implementations, the illumination device 2000 can include one ormore optical conditioners 2501 disposed below the lower surface 2105 ofthe light guide 2101. The one or more optical conditioners 2501 canreceive light that is output from the light guide 2101 through the lowersurface 2105 and shape, condition, or redirect the output beam of light.In some implementations, the one or more optical conditioners films 2501include one or more lenticular structures or films (for example, astructure or film with one or more elongated lenticules, or one or moresymmetric or asymmetric lenses or lenslets, such as angle-spreading filmsheets 52 and 53 of FIG. 1D or other similar films disclosed herein)and/or one or more light turning films (for example, a prismatic typefilm with the apex of each prismatic feature facing the light guide2101, such as facetted film 982 of FIG. 30E or other similar filmsdisclosed herein). In some implementations, an optical conditioner 2501can include one or more layers or structures. For example, an opticalconditioner 2501 can be a stack.

As mentioned above, in some implementations, the illumination device2000 can be configured to doubly collimate light emitted from the one ormore light sources 2203. For example, light ray segments 2401 may beemitted by the one or more light sources 2203 toward the optical coupler2301. Thereafter, the curved sidewalls or surfaces 2303 of the opticalcoupler 2301 may redirect the light collimate the ray segments 2401 in aradial direction to inject the light into the light guide 2101 so thatthe light propagates toward the periphery of the light guide. The lightcontinues to propagate inside the light guide 2101 via total internalreflection until the light exits as described in reference to FIG. 35C.As disclosed elsewhere herein, in the absence of a light-turning orlight-extracting sheet, the light will exit the light guide at anoblique angle. Therefore, in some implementations, a reflective surfacemay be disposed adjacent to the upper surface 2103. For example, areflectorized light-turning film having prism-like facets may bedisposed adjacent to the upper surface. In other implementations, atleast a portion of the upper surface 2103 may be reflectorized withoutprism-like facets. A light-turning film may then be disposed at theoutput surface, illustrated here as the lower surface 2105. In such animplementation, light exiting the light guide 2101 at an oblique angleis then turned by the light-turning film to exit the illumination device2000 at a desired angle, for example, as illustrated by ray 2405,orthogonal to the lower surface 2105.

As discussed herein, the light guide 2101 can be tapered to provide forcollimation of the beam in a meridional plane along a radial direction.For a radially symmetric light guide 2101, the light is thereforecollimated along a large number of intersection meridional planes. Insome implementations, the ray segments 2405 exiting the light guide 2101may by disposed within an angular range +/−φ, measured as full widthhalf maximum, relative to the longitudinal axis. The angular range +/−φcan be based at least in part on the taper angle α. For example,assuming no etendue preserving angle transformers pre-collimating thelight, and assuming no output angle spreading film (such as a lenticularfilm) and ignoring the effect of any light-turning films, when the taperangle is between about 1 and 4 degrees, the output beam full width athalf maximum may be between ±2 and ±4 degrees. If the input light ispre-collimated in a range between ±15 to ±30 in the light guide, theoutput beam width may be even narrower.

FIG. 35E shows a cross-sectional view of an example lighting device 3000including the tapered light guide 2101 of FIG. 35D. As with theillumination device 200 of FIG. 35D, the light guide 2101 of theillumination device 3000 includes a light entry surface 2107 formed by acolumnar recess 2106 disposed near a center portion of the light guide2101. However, in this implementation, the illumination device 3000includes a plurality of light sources 2203 offset angularly from oneanother about the longitudinal axis of the illumination device 2101. Inthis way, each light source 2203 is configured to emit light directlyinto the light guide 2101 through the light entry surface 2107.

FIG. 35F shows a cross-sectional view of an example lighting device 4000including the tapered light guide 2101 of FIGS. 35D and 35E. In thisimplementation, the illumination device 4000 includes a plurality oflight sources 2203 disposed angularly about the longitudinal axis of theillumination device 2101. In some implementations, the plurality oflight sources 2203 can be mounted on an optical coupler 2301 including aplurality of curved surfaces 2303. As illustrated, the plurality oflight sources 2203 can each face in a radial direction and the curvedsurfaces 2303 of the optical coupler 2301 can shroud the light sources2203 to direct ray segments 2403 emitted from the light sources 2203 inthe radial direction. Each optical coupler 2301 can include a reflector,for example, an etendue preserving reflector. In some implementations,the reflector can improve the collimation of light for injection intothe light guide 2101 through the light entry surface 2107. In this way,light emitted from the light sources 2203 can be injected directly intothe light guide 2101 in a radial direction from the light sources 2203and/or can be coupled into the light guide 2101 in a radial direction bythe optical coupler 2301.

FIG. 36A is a partial cross-sectional perspective view revealinginternal details of the thin emitter-reflector-light guiding plateillumination system 1 elements of FIG. 35A, but along with an example ofone type of radial heat extracting element 1192 useful in suchconfigurations. Thickness 1194 of radial heat extracting element 1192 isonly meant illustratively, and depends on the operating wattage of LEDemitter 1000, the efficiency with which sink and emitter substrate arethermally attached, the sink material, the dynamics of ambient airflow,and the details of the extracting element's thermal design. The diameter1196 of this particular light engine example of this disclosure ischosen as 95.25 mm (3.75 inches), which is a common diameter fortraditionally circular light bulbs. The central coupling diameter 1198in this example, 7.2 mm, has been matched to the characteristics of thesix-chip Osram OSTAR™ model LE CW E3A being used as an example, andcould be made smaller or larger with other LED emitter designs andcoupling arrangements.

FIG. 36B is a schematic perspective view of the illustrative lightengine implementation represented in FIG. 36A, without thecross-sectional detail of FIG. 36A, and in a down-lighting orientation.This perspective reveals an illustrative means of providing insulatedtubular electrical conduit 1200 for electrical interconnections to andfrom the interior terminals 1062 of LED emitter 1000, and the associatedelectrical connecting pins 1202 and 1203. Tubular conduit 1200 may besubstantially hollow, and may be an integral part of heat extractingelement. FIG. 36C is a schematic perspective view similar to that ofFIG. 36B showing the illustrative light engine implementation of FIGS.35A-35C and 36A-36B and its intrinsically well-collimated far-fieldoutput illumination 1206. Computer ray trace simulations of this designshow a circular beam profile 1208 in the far field with angular extent1210, +/−θ_(c) being approximately +/−6 degree (FWHM), with a soft haloout to about +/−9 degrees.

FIG. 36D is an exploded perspective view of the light engine representedin FIG. 36B, adding parabolic lenticular film sheets (1212 and 1213)plus a circular frame 1214 to retain them. The parabolic lenticular lenssheets 1212 and 1213 are the same orthogonally-crossed angle-changingelements described earlier (for example, film elements 874 and 875, FIG.28) with the lenticules of each film sheet 1212 and 1213 which can facetowards the light engine's output surface 1157. Circular frame 1214 isadded to retain the two sheets. In this example, linear extruded filmsheets 1212 and 1213 are cut into circular disks for easiest mounting.

FIG. 36E shows the unexploded view of the thin system 1 of FIG. 36D.

FIG. 36F is a schematic perspective view similar to that of FIG. 36C butshowing the asymmetrically widened far field output illumination 1220 ofthe thin illumination system 1 shown in FIG. 36E. Computer ray tracesimulations of this design, show that the addition of the two crossedlenticular angle changing films of this disclosure, in this example eachhaving deliberately different angle-changing characteristics (onewidening the intrinsic +/−6 degree illumination to +/−30 degrees in theZX meridian, and the other widening the +/−6 degree illumination to only+/−15 degrees in the orthogonal ZY meridian) produce the intendedsubstantially rectangular beam profile 1222 in the far field withangular extents 1224 and 1226, +/−θ_(X) being approximately +/−30-degree(FWHM), with practically no halo beyond that, and +/−θ_(Y) beingapproximately +/−15-degree (FWHM), with practically no halo beyond that.In this implementation, the crossed linear extruded lenticular lenssheets 1212 and 1213 (hidden in FIG. 36F), transform the circularlysymmetric near field light 1228 into rectangular far field light 1222.

FIG. 36G shows the illustrative far field beam pattern from the thinillumination system 1 of FIG. 36F placed at a 1500 mm height above the1800 mm×1800 mm surface to be illuminated. The computer simulated fieldpattern 1230 spreads about +/−30 degrees along x-axis 7 +/−15 degreesabout y-axis 5, both FWHM.

Some examples of the thin illumination systems disclosed herein canutilize one or more low-voltage DC operating LED emitters as theirinternal source of light. It is feasible to use any of the foregoinglight engine examples (e.g., FIGS. 1A-1D, 2A-2E, 3A-3B, 4, 12B-12C, 26,28, 30A, 30C, 31A-31B, 32A-32B, 33A-33C, 35A-35F, 36B-36F, and 37A-37G)with a high voltage AC power source, provided the high voltage AC powersource is properly converted to low-voltage DC and suitably regulated,prior to its interconnection with LED emitters 3, 904 and 1000.

A potentially practical commercial reason for doing this is presented bythe light engine example of FIGS. 36B-36F. Such a thin circulardirectional illumination system when fitted with a suitable AC-to-DCconverting stem attachment terminated with standard light-bulb stylescrew cap, may be deployed usefully as a screw-in retrofit type LEDlight bulb. Although some implementations disclosed herein illustrateillumination devices having multiple electrical connections (forexample, FIGS. 35D-35F and FIGS. 37B-37G), a person having ordinaryskill in the art will appreciate that such electrical connections can beelectrically coupled to a screw cap or other electrical coupling forconnecting the device to a source of power. The far field illuminationfrom at least some of the thin light engines made according to thisdisclosure can exhibit particularly sharp angular cutoff outside theintended angular extent. This behavior is associated generally withreduced off-angle glare and more efficient field utilization in lightbulbs used in spot and flood lighting applications.

FIG. 37A is a schematic perspective view illustrating one possible wayof adapting the thin profile light engine example of FIG. 36E as ascrew-in style light bulb. In this illustration, the necessary AC-to-DCconversion electronic parts are housed (and not shown) within adapterstem 1232. Adapter stem 1232 is thermally coupled to radial heatextracting element 1192, electrically interconnected to insulatedtubular electrical conduit 1200 and fitted with standard light bulbstyled screw cap 1234. The thin profile light engine example of FIG. 36Emodified only with decorative bezel and affixation hardware may beapplied directly in conventional recessed can applications. Of course,other thin profile light engines disclosed herein can be coupled to theadapter stem 1232. For example, the implementations of FIGS. 37B-37F canoptionally be coupled to an adapter stem or installed directly within alight fixture recess.

The radially constrained extrusion of tapered light guiding plate 1160,as described by FIGS. 34C-34D, leads to the circular light guiding plategeometries illustrated. As mentioned above, it is both possible andpractical, however, to convert the circular light guiding plate form ofthis disclosure into a related square and rectangular form. The linearlyextruded square and rectangular light guiding plates 112 and 1034 usedin the light engine examples of FIGS. 30A, 30C, 31A-31B, 32A-32B, and33A-33C must have a linear LED emitter input coupling means, which inturn extends the resulting light engine's lateral dimensionsproportionally. The radial form described by FIGS. 36A-36F serves toencapsulate the LED emitter between the tapered light guiding plate andthe heat extractor, which can be a desirable feature.

FIG. 37B shows a perspective view of an example illumination device 5000a including a heat extracting element 2600, an electronics chassis 2701,and a light guide 2101 having a polygonal cross-sectional shape. In someimplementations, the light guide 2101 can have a square or rectangularcross-sectional shape and can be tapered in a radial direction similarto the illumination devices discussed above with reference to FIGS.35A-35F. That is to say, the light guide 2101 can include an uppersurface 2103 and a lower or illumination surface 2105. The upper surface2103 and the lower surface 2105 can meet at a peripheral edge 2109(schematically depicted as having a thickness for illustrative purposes)and can define a taper angle therebetween. In some implementations, thetaper angle can be between 1 degrees and 15 degrees, for example,between 2 degrees and 8 degrees. One implementation of a square-shaped,radially-tapered light guide is illustrated in FIGS. 39A-39D

In some implementations, the electronics frame or chassis 2701 can bedisposed between the light guide 2101 and an electrical coupling 2703.The electrical coupling 2703 can include two electrical connections2705, for example, and may be configured to electrically and/ormechanically couple the illumination device 5000 a to an electricalconnection of a lighting fixture, for example, an electrical socket. Insome implementations, the electrical coupling 2703 can include a GUsized connector or Edison screw-type connector. In some implementations,the electrical frame or chassis 2701 can house and/or contain individualcomponents of the illumination device 5000 a. For example, theelectronics chassis 2701 can house power controlling electronic circuitsthat are electrically coupled to the electrical coupling 2703 and topositive and negative electrical connections of one or more lightsources of the illumination device 5000 a.

In some implementations, the electronics chassis 2701 can house the oneor more light sources of the illumination device 5000 a. For example,the electronics chassis 2701 can house one or more LED sourcesconfigured to input light into the light guide 2101. In otherimplementations, the electronics chassis 2701 can be disposed betweenthe one or more light sources of the illumination device 5000 a and theelectrical coupling 2703.

As shown, the heat extracting element 2600 can include a plurality offins 2601 configured to dissipate heat from the one or more lightsources and/or from the light guide 2101 of the illumination device 5000a. In some implementations, the fins 2601 can include pins or rodsprotruding upwards. In some implementations, the fins 2601 are sized andshaped to provide sufficient surface area to dissipate heat generated bythe illumination device 5000 a. Further, in some implementations, theheat extracting element 2600 can include one or more channels orpassages to allow for the passage of a heat transfer fluid, for example,air, between the fins 2601. In this way, the one or more channels orpassages may allow for convective heat transfer between the heatextracting element 2600 and the fluid passing there over. In someimplementations, the device 5000 a may include one or more active heattransfer structures, for example, one or more fans or piezoelectricdevices. Such structures can mechanically flap, flex, or otherwiseactuate to create a current or flow of fluid through and/or over atleast a portion of the illumination device 5000 a.

As discussed below, the illumination device 5000 a may be installedwithin confined recesses of a light fixture and the heat extractingelement 2600 may prevent the illumination device 5000 a from overheatingwithin the recess, in some implementations. Although illustrated on theperiphery of the electronics chassis 2701, in some implementations theheat extracting fins 2601 can be disposed in the middle of theillumination device 5000 a and the components housed within theelectronics chassis 2701 can be disposed on the periphery of the device.

FIG. 37C shows a perspective view of an example illumination device 5000b including the heat extracting element 2600 of FIG. 37B, theelectronics chassis 2701 of FIG. 37B, and a light guide 2101 having acurvilinear cross-sectional shape. In some implementations, the lightguide 2101 can have a circular or round cross-sectional shape.

As with the light guide 2101 of the illumination device 5000 a, thelight guide 2101 of the illumination device 5000 b can be tapered(radially relative to the longitudinal-radial plane). In someimplementations, the upper surface 2103 and the lower surface 2105 candefine a taper angle therebetween along a peripheral edge 2109. In someimplementations, the taper angle can be between 1 degree and 15 degrees,for example, between 2 degrees and 8 degrees.

In the illumination devices 5000 a and 5000 b of FIGS. 37B and 37C, thelight guides 2101 can have maximum radial dimensions that are greaterthan maximum radial dimensions of the heat extracting element 2600. Inthis way, the light guides 2101 can extend outwardly in the radialdirection from the heat extracting elements 2600 and from theelectronics chasses 2701. In some implementations, the heat extractingelements 2600 and electronics chasses 2701 may be sized and shaped tofit within the recess of a given lighting fixture while the light guides2101 may not fit within the recess and may extend outwardly in theradial direction from an opening to the recess.

FIG. 37D shows a side view of the example illumination device 5000 b ofFIG. 37C illustrated with an example light fixture 6000. In thisimplementation, the example light fixture 6000 can include a can 6102that is recessed relative to tiles 6103 to form a recess 6101. Thus, thelight fixture 6000 can be considered a “can fixture.” In someimplementations, the tiles 6103 can form part of a ceiling to provideoverhead lighting from an illumination device, for example, illuminationdevice 5000 a or 5000 b, installed within the light fixture 6000. Asshown, an electrical connection can be disposed at an end of the recess6101 that is opposite to the surface 2101 and the electrical connectioncan electrically and/or mechanically engage the electrical connectionsof the illumination device 5000 b to electrically and/or mechanicallycouple the illumination device 5000 b to the light fixture 6000.

Still referring to FIG. 37D, the light fixture 6000 can have an openingthat is defined by an opening between the tiles 6103 of the lightfixture 6000. The opening can have a maximum radial dimension D₁. Insome implementations, the light guide 2101 can have a maximum radialdimension D₂ that is greater than the maximum radial dimension D₁ of theopening of the can 6102. In this way, the illumination device 5000 b canbe electrically and/or mechanically coupled with an electricalconnection of a given light fixture 6000 even though the light guide2101 may not fit within the can 6102 of the light fixture 6000.Accordingly, an existing lighting or illumination system or architecturemay be retrofit or converted to use the illumination devices providedherein even through a light guide of such an illumination device doesnot fit within the can or recess of the light fixture. As a result, insome implementations, an illumination device having a light guide thatis larger than a recess or can of a light fixture may be utilized toprovide a larger and/or more luminous output beam than a lighting devicethat is configured to fit within the recess.

Further, the can recess 6101 can have a height or depth dimension hmeasured between a surface of the can 6102 that contacts the electricalconnections of the illumination device 5000 b and the tiles 6103. Insome implementations, the height h of the recess 6101 can be less than 2inches, for example, less than 1 inch, less than 0.5 inches, or between0.25 and 0.5 inches. In some implementations, the electrical connectionsof the illumination device 5000 b can be disposed on one or more sidesof the device, for example. In this way, the height h of the can 6102can be further limited. In some implementations, a can may be modifiedwith a stem, for example, the stem illustrated in FIG. 37A, such that acan having a height or depth dimension greater than the depth dimensionh of the can 6102 can be electrically coupled to the illumination device5000 b with the light guide 2101 disposed outside of the opening.

FIG. 37E shows a perspective view of an example illumination device 5000c including the heat extracting element 2600 of FIG. 35G, theelectronics chassis 2701 of FIG. 37B, and a light guide 2101 having asize and shape that matches the profile of the electronics chassis 2701.FIG. 37F shows a side view of the example illumination device 5000 c ofFIG. 37E illustrated with the example light fixture 6000 of FIG. 37D. Asshown, in some implementations, the light guide 2101 can have a maximumradial dimension D₂ that is less than the maximum radial dimension D₁ ofthe opening of the can 6102. In this way, the illumination device 5000 ccan fit within the recess of the light fixture 6000. In someimplementations, the light guide 2101 may be sized and shaped such thatthe illumination device 5000 b can be installed within a light fixtureintended to receive another illumination device, for example, a PAR64,PAR56, PAR46, PAR38, PAR36, PAR30, PAR20, and/or PAR16 device, and thelight guide 2101 can provide an output beam that matches anotherillumination device configured to fit within the can 6102. Accordingly,an existing lighting or illumination system or architecture may beretrofit or converted to use the illumination devices provided hereinwithout changing the illumination properties or characteristics of thesystem even through the light fixtures were initially intended to beused with differently configured lighting devices. As mentioned above,in some implementations, a can may be modified with a stem, for example,the stem illustrated in FIG. 37A, such that a can having a height ordepth dimension greater than the depth dimension h of the can 6102 canbe used with the example illumination device 5000 c.

FIG. 37G shows a side view of an example illumination device 5000 dillustrated with an example light fixture 7100. The light fixture 7000includes a recess 7101 formed relative to a decorative ceiling surface7103. The illumination device 5000 d includes a heat extracting element,and a light guide 2101. In some implementations, the illumination device5000 d can also include one or more light sources (not shown) configuredto emit light into the light guide 2101, for example, as discussedherein with respect to any light guide that is configured to receivelight from one or more light sources. The one or more light sources maybe electrically and/or mechanically coupled to the light fixture 7100 bya pendant, chain, or wire 2901 that extends at least partially betweenthe one or more light sources and an electrical coupling 2703. As shown,the electrical coupling 2703 can be disposed within the recess 7101 ofthe light fixture 7000 and can be electrically and/or mechanicallycoupled to a socket 7105 of the light fixture 7000 by one or moreelectrical connections 2705. In this way, the light guide 2101 of theillumination device 5000 d can be suspended or hung from the decorativeceiling surface 7103 of the light fixture 7000. Thus, in someimplementations the illumination device 5000 d can be utilized as achandelier, for example.

As discussed above, the light guide 2101 may be tapered and may berelatively thin. For example, the light guide 2101 may have a maximumlongitudinal dimension that is between about 1 mm and about 16 mm, forexample, between about 2 mm and about 6 mm. Thus, the light guide 2101may weigh less than existing chandeliers that do not include thethin-profile tapered light guides disclosed herein.

In some implementations, the light weight of the light guide 2101 canallow the illumination device 5000 b to be suspended or hung directlyfrom the decorative ceiling surface 7103, such as a ceiling tile, forexample, rather than a structural utility ceiling. For example, amounting plate 2903 can be coupled with the decorative ceiling surface7103 by one or more fasteners and/or adhesive materials. The mountingplate 2903 can serve to distribute the relatively low load of the lightguide 2101 and heat extracting element 2600 to the decorative ceilingsurface 7103 without requiring an engagement within a utility ceilingdisposed above the decorative ceiling surface 7103. In this way, theillumination device 5000 d can be used as a chandelier with existinglight fixtures configured to receive and support non-chandelier typelighting devices without requiring structural modifications to the lightfixtures.

Unfortunately, simply trimming the circular light guiding plate to asquare or a rectangle form, sacrifices a substantial percentage of lightoutput efficiency. The reason for this truncation inefficiency can beseen in the illustrations of FIGS. 38A and 38B.

FIG. 38A is a schematic perspective view of a square truncation 1240 ofthe radially constrained light guiding plate extrusion illustrationshown previously in FIG. 34C. It can be seen that many of the taperedcross-sections are clipped off prematurely by this truncation beforethey can reach their full taper length when the taper becomes anidealized knife-edge like those in the linear extrusions of FIG. 34A orthe radial extrusions of FIG. 34C. In the truncation of FIG. 38A, idealcross-sectional behavior only occurs on the diagonals of the inscribedsquare. Elsewhere, the tapered cross-sections are clipped off earlier.The consequence of having truncated cross-sections in an efficientlymade light guiding plate is undesirable light loss from thickened edgesof the truncated plate.

FIG. 38B is magnified section view 1242 of the complete schematicperspective provided in FIG. 38A, better illustrating the significanceof edge-thickening defects caused by premature truncation. It is readilyseen that tapered cross-section 1244 come to almost an ideal knife-edge,but that tapered cross-section 1246 is truncated to substantiallygreater edge thickness 1248.

The remedy for this inefficient taper truncation is a combination ofradial and linear boundary constraints, enabled by a variable taperlength and taper angle. Rather than forcing the taper cross-section toremain constant in length (and associated taper angle), both the taperlength and angle are permitted to vary subject to corresponding radialand linear extrusion constraints. In this manner a radially extrudedsquare (or rectangular) light guiding plate joins light guiding plates.

FIG. 39A illustrates a radially and linearly constrained extrusion withfive prototype taper cross-sections 1250-1254, swept in a 90-degreeradial arc segment 1256 about axis line 1148 (running parallel to systemZ-axis 6). While the taper cross-sections sweep radially about axis line1148 and arc 1256, their zero-thickness idealized knife-edges areconstrained to follow linear extrusion axis 1258.

FIG. 39B is a perspective view illustrating the extrusive combination offour of the 90 degree segments as developed in FIG. 39A.

FIG. 39C is a perspective view, similar to that of FIG. 34D, butillustrating the quad-sectioned square tapered light guiding plate 1260that results from the radially and linear constrained extrusion of FIG.39C. This square light guiding plate 1260 is radially fed with LEDemitter input light through the same cylindrical entry surface 1154 asdeveloped for circular light guiding plate 1160 in FIG. 34D. Similarly,pentagonal, hexagonal, and octagonal shaped tapered light guiding platescan be made using five-, six-, and eight-sectioned light guide plates inways similar to those discussed above for a square shaped light guideplate.

One implementation resembling the quadrant shown in FIG. 39A, can beproduced by linearly extruding cross section 1252 along Y-axis 5 in bothdirections (as if creating a rectangular plate) and then chopping italong the planes defined by 1254 and 1250. This extrusion would bydefault create a linear input face rather than one curved about axis1148, though the input face could be easily made curved by simplecut-out. Four of these quadrants could then go together just as in FIGS.39B-39C, with somewhat simpler surface topology but still meeting theknife edge requirement required for maximum efficiency and still havingsimilar appearance.

Another implementation uses just the one quadrant of FIG. 39A combinedwith a source and coupling optic that send light substantially into theinput face of that one quadrant.

Yet another implementation can be created simply by bifurcating thequadrant of FIG. 39A at the plane defined by cross section 1252,creating two substantially triangular half-quarters, and joining the twohalf-quarters at the surfaces defined by 1250 and 1254 to create onesquare quadrant (as opposed to the triangular quadrant shown). This canbe combined with a source and coupling optic that send lightsubstantially into the input face of that one quadrant.

In each of the latter three implementations, the plates can be combinedwith substantially the same circular turning films (cut to size)introduced in FIGS. 34E-34F to produce highly collimated light. Whilethe collimated far-field pattern in each case will not be identical tothat of the circular disk of FIG. 35A-35C, the use of previouslydiscussed beam-spreading films (for example, shown in 36D) can producesubstantially many of the same far-field patterns possible with theother linearly and radially extruded engines described above.

FIG. 39D is a perspective view of a thin square light engine form thatuses a square lighting guiding plate 1260 (hidden), and an otherwisesimilar internal arrangement to that of the circular light engineexample shown in FIG. 36E. Square cut lenticular film sheets 1262 areretained in frame 1264. Radial heat extracting element 1192 is deployedin this example as square heat extracting element 1266. Whileimplementations based on radially extruded light guiding plates andlight extraction films can be useful, there is one illuminationattribute that is unique to the linearly extruded light guiding andlight extracting forms described above. The linearly extruded lightguiding systems (for example, those represented in FIGS. 3A-3B, 4, 26,28, 30A, 30D, 31A, 31D, 32A-32B, and 33A-33C) have the capacity toprovide collimated illumination at an oblique angle to the light guidingplane, potentially providing an unobtrusively compact means of obliqueillumination.

FIG. 40A shows a perspective view of another implementation of thesingle-emitter form of the thin illumination system 1 deploying atapered light guiding pipe system 120 as its input engine that iscross-coupled with tapered light guiding plate system 1992 using a planetop mirror 1990. A generalized description of tapered light guidingsystem 1990 was shown earlier in FIG. 3A as 110 with a facetted lightextraction film. In this particular example, the system's facettedreflecting prisms 116 (as in FIG. 3A) are replaced with a specularlyreflecting plane mirror 1990. This modification is equivalent to makingthe total included apex angle 352 of the reflecting prisms used in FIG.3A and described in the details of FIG. 11A approach 180 degrees.

FIG. 40B is a side cross-sectional view of FIG. 40A, similar to thatshown earlier in FIG. 8B, except that FIG. 8B applied only to the inputengine, collimating light in just the one meridian shown. Thisimplementation collimates output light in both meridians, and along withuse of optimized input light 1994 (in air) and 1996 (in light guide 112)from RAT reflector 114 (illustratively +/−52.5 degrees in air) theoverall illumination system 1 develops a more smoothly shaped far fieldoutput beam profile 1998. All dimensions and materials follow thepreviously established ongoing example, which set illustrative 3 mmplate thickness (THKP 156) and illustrative 3 mm pipe thickness (THKB150), both as in FIG. 4, 3 degree pipe and plate taper angles,approximately 50 μm knife edge thickness, polycarbonate pipe 100 andpolycarbonate plate 112 (which as described above, may be made of PMMA).Reflector 1990 is attached to the illustrative 57 mm×57 mm tapered lightguiding plate 112 as discussed earlier, by an acrylic layer havingrefractive index between 1.47 and 1.49.

FIG. 40C is a perspective view of the illumination system of FIGS. 40Aand 40B showing the collimated nature of the obliquely directed farfield output beam the system produces. Dotted outline 2010 helps invisualizing the beam character.

FIG. 41A is a side elevation showing the deployment of the illuminationsystem 1 of FIGS. 40A-40C mounted a vertical distance of 10 feet (about3000 mm) 2020 above ground level 1022 and a horizontal distance of 3feet (about 900 mm) 2024 from a vertical wall surface 2026 to beilluminated by the obliquely-directed far field output beam 1990 comingfrom this type of thin-profile illumination system 1. The associatedbeam pattern on wall surface 2026 is displaced downward from theluminaire system's horizontal mounting plane by 1.82 feet (about 550 mm)2028 because of the approximately 27-degree beam direction establishedin FIG. 40B (for the illustrative conditions).

FIG. 41B shows a front view of wall surface 2026 and beam pattern 2030made by illumination system 1 of the present example. Beam pattern 2030retains its approximately +/−5-degree angular extent in the horizontalplane, but is broadened in the vertical direction to about +/−10 degreesby the projection caused by its oblique angle of incidence. Theassociated horizontal and vertical brightness profiles are designated2032 and 2034.

FIG. 42 is a perspective view of another implementation similar to FIG.31C, but adding one variation, the application of a one-dimensionalangle-spreading lenticular filmstrip 1036 to input edge 121 of lightguiding plate 112 to widen the outgoing beam's 2038 horizontal angularextent.

FIG. 43A illustrates the side elevation of a wall and floor systemincluding the illumination system of FIG. 42. It further illustratesthat despite the addition of angle-spreading film 2036 to the input edgeof light guiding plate 112, the obliquely directed far field beam crosssection 2038 and the rest of the side elevation layout, is identical tothat of FIG. 41A in this example.

FIG. 43B shows a front view of wall surface 2026 and beam pattern 2040made by illumination system 1 of the present example. Beam pattern 2040is broadened in the vertical direction to about +/−10 degrees, asbefore, by the projection caused by its oblique angle of incidence, buthas been broadened deliberately to +/−24 degrees as shown by thelenticular angle-spreading film that is used. The associated horizontaland vertical brightness profiles are designated 2042 and 2044.

FIG. 44 is a side view of yet another implementation based on thevariations of FIGS. 40A-40C, 41A, 42 and 43A, but adding an externaltilt mirror, 2050, to receive the obliquely-directed output illumination1998 (or 2038) from this variation of illumination system 1, andredirecting that illumination 2038 back towards another vertical surface2052 to be illuminated, as in redirected beam profile 1052. Themathematical relationship between all elements is based on geometry, andthe necessary symbols are provided clearly on FIG. 44 in full detail.The mirror length (BD+DF), LM, is determined by the extreme field angle,P_(k), which for the present example is β_(f)=θ_(w)+∈_(b), ∈_(b) beingthe extracted beam's half width, 32.8 degrees. Length BC=LP (Tan β_(f)).Offset length CE=LP (Tan β_(f)) Tan γ_(T), CD=BC (Sin γ_(T)). BD=BC (Cosγ_(r)). Then in triangle CEF, the third angle is 180−β_(f)−(90+γ_(T))=90 −β_(f)-γ_(T). So, DF=CD (Tan 90 −β_(f)−γ_(T)). And,LM=BD+DF=(BC)(Cos γ_(T))+(BC(Sin γ_(T)))(Tan 90 −β_(f)−γ_(T))=LPTan(β_(f)) [Cos(γ_(T))+Sin γ_(T) Tan(90 −β_(f)−γ_(T))]. The numericalvalues shown in FIG. 44 are for an illustrative mirror tilt, γ_(T), of12 degrees.

The degree to which tilt mirror 2050 is tilted with respect to thesystem's vertical z-axis 6, γ_(T) above, and the separation distance2054 between the system's tilt mirror and the surface to be illuminated,collectively determine how far down the opposing vertical surface willthe resulting illumination pattern be situated.

FIG. 45A is a side elevation showing the deployment of this variation onillumination system 1 mounted 10 feet above ground level 2022 and ahorizontal distance of 3 feet from a left hand vertical wall surface2060 to be illuminated by the obliquely-directed far field output beam2062 coming from this tilted-mirror version of this thin-profileillumination system 1. The associated beam pattern 2064 on wall surface2060 is displaced downward about 3.7 feet from the luminaire system'shorizontal mounting plane because of the 12-degree tilt placed on tiltmirror 2050. The resulting pattern shift for this 12-degree tilt isapproximately 3 Tan(2γ_(T)+φ_(W))=3 Tan(51)=3.7 feet.

FIG. 45B shows a front view of left-side wall surface 2056 and beampattern 2070 made by illumination system 1 of the present example. Beampattern 2070 retains its horizontal plane broadening from lenticularinput film 2036, but shifted downward by the action of tilt mirror 2050and its 12-degree tilt in this example. The associated horizontal andvertical brightness profiles are designated 2072 and 2074.

FIG. 46A is a side elevation identical to FIG. 45A, but for the case ofa 16 degree mirror tilt. The associated beam pattern 2080 on wallsurface 2060 is displaced downward about 5 feet from the luminairesystem's horizontal mounting plane because of the 16 degree tilt placedon tilt mirror 2050.

FIG. 46B is the same representation as FIG. 45B, but for the case of a16 degree mirror tilt and its associated beam pattern 1080. Theassociated horizontal and vertical brightness profiles are designated2082 and 2084.

FIG. 47 is a perspective view of the corner of a room, showing twowalls, a floor, and a framed painting illuminated obliquely by thethin-profile tilted mirror illumination system for the case illustratedin FIGS. 46A and 46B representing a 16 degree mirror tilt.

The implementations shown in FIGS. 40A-40C, 41A, 42, 43A, 44, 45A, 46Aand 47 represent just one of numerous possible examples. Rather thanusing plane mirror 1990 (FIG. 44), in combination with tilted mirror2050 (FIGS. 44, 45A and 46A), faceted prism sheet 114 could be arrangedwith the equivalent facet angles to generate the same illuminatingoutput beam direction (via the beam redirecting implementations of FIGS.11A, 11B, 18, 19 and 20). Moreover, the multi-element array-type inputengine (FIGS. 2A-2C, 31A, 31B, 32A, 32B, and 33A-33C) may be substitutedwhen applications call for higher lumen output from a single luminaireunit, as they might in various high intensity spot lighting uses, or adifferently arranged grouping of light engines facilitated byindividualized LED emitter engine segments.

FIG. 48A shows yet another implementation similar to that of FIG. 42,adding a one-dimensional angle-spreading lenticular filmstrip 2036 toinput edge 121 of light guiding plate 112 to widen the outgoing beam's2100 horizontal angular extent, but using a prism sheet rather than aplane mirror atop tapered light guiding plate 112.

FIG. 48B shows the configuration of FIG. 48A in perspective view.

FIG. 48C is another perspective view of FIG. 48A, showing theillumination system's underside output aperture, along with itsresulting near field spatial brightness uniformity 2104 and the darkfield area 2106 occurring nearest the beginning region of its LED inputengine.

FIG. 49 is a perspective view illustrating the behavior of thetapered-version of the light guiding input engine 120, showing graphicsimulation 2110 of angular extent of the light condition at the start oflight guiding pipe 100, and a graphic simulation sequence 2111-2115 ofthe subsystem's output light at various points along the light guidingpipe's output edge. It can be seen that despite the optimum choice ofthe angular distribution of input light at the start of the lightguiding pipe, the subsystem fails to maintain constancy of the outputlight angular extent. Output light nearest the start of the lightguiding pipe shows a substantially reduced angular range, and doesn'tstabilize the expected angular distribution until nearly the midpoint.This misbehavior (or deviation from ideality) gives rise to the nearfield non-uniformity shown in FIG. 48C.

One solution to the near field spatial non-uniformity comes from FIGS.42 and 48A and 48B. These illustrations show that the deployment of alenticular lens sheet, lens axes aligned perpendicularly to the longlength of the light guide plate's edge, is successful in widening theoutgoing beam's corresponding angular extent. It stands to reason thatbecause of this, smaller portions of lenticular lens film may be appliedto boost the angular content of a deficient angular width just enough tomake it right.

FIGS. 50A, 50B, 50D, 50F and 50G all show various lenticular filmsection configurations that have been simulated. In each case, not onlyhas the size and shape of the lenticular section been varied, but so hasthe strength (optical power) of the parabolic lenticules.

The success of this idea in improving the evenness of near fielduniformity is demonstrated in the perspective views FIGS. 50E and 50H.The optimization shown in FIGS. 50A-50D, 50F and 50G all show variouslenticular film section configurations that have been simulated.

For specialty applications such as LCD backlighting, where visualappearance of the near field illumination is more critical, improvementssuch as are summarized in FIGS. 51A-51C are available as well. In thissequence, the spacing of the prisms in light extraction film applied tothe light guiding plate is adjusted to fine tune the degree of nearfield spatial non-uniformity.

FIG. 51A shows the underlying concept of this variable prism spacingmethod, using a conveniently enlarged prism coarseness to help displaythe design intent. The bands without prisms do not extract output light,and can be used to dilute regions having excess brightness. Since prismperiods are best below the levels of visual acuity, the use of darkbands will not interfere with viewing quality.

FIG. 51B shows a perspective view of the design concept illustrated inFIG. 52A.

FIG. 51C shows a perspective view of a thin illumination system 1 withsuccessfully homogenized near field using the variable prism spacingmethod.

FIG. 52 shows a graphical comparison of near field spatialnon-uniformity of one thin profile illumination system partiallysuccessful angular input edge correction as in FIG. 50H and one with thecomplete correction illustrated in FIG. 51C via the variable-prismspacing-method. A graphic simulation of the near field uniformity 2146shows considerable smoothness compared with simulation 2130 if FIG. 52E.

FIGS. 53A-53E show examples of cross-sectional schematic illustrationsof various stages in a method of manufacturing an illumination deviceincluding a transparent structure. While particular parts and steps aredescribed as suitable for fabricating certain implementations of anillumination device, for other implementations, different parts andsteps, and materials can be used, or parts can be modified, omitted, oradded.

In FIG. 53A, a substrate layer 8001 has been provided and in FIG. 53B abacking layer 8003 has been provided and patterned on the substratelayer 8001. As shown, the backing layer 8003 can be formed to include alower surface 8006 and an upper surface 8004. The upper surface 8004 andthe lower surface 8006 can meet near a center portion 8002 of thebacking layer 8003 and define a taper angle α therebetween. In someimplementations, where the backing layer 8003 will remain attached to atransparent layer for support, the backing layer 8003 can be a highlyreflective material, for example, a silver coated or high reflectivityfilm such as 3M ESR film coated structure. In some implementations, anoptically clear epoxy or optically coupling/clear epoxy can be used tobone the transparent layer to the backing layer 8003 to reduce air gapstherebetween. Also, clear bonding agents, for example, silicone or PSAhaving a refractive index between 1.42 and 1.47 could be used. In someimplementations, the backing layer 8003 can be part of a chuck used toform the transparent structure. In other implementations, the backinglayer 8003 and the transparent structure can be removed together fromthe substrate layer 8001. In such implementations, the transparentstructure can remain tapered by virtue of a reflective surface betweenthe backing layer 8003 and the transparent structure, but physically,the transparent structure and backing layer 8003 may appear together asa disk or truncated column to support a narrow, low angle taperedtransparent structure.

FIG. 53C illustrates providing a transparent layer 2101 a over thebacking layer 8003 and the substrate layer 8001. In someimplementations, the transparent layer 2101 a includes a transparentoptical quality dielectric material, for example, polycarbonate orpolymethyl methacrylate (also referred to as PMMA or acrylic). In someimplementations, the transparent layer 2101 a can be formed using amolding process, for example, casting, injection, orcompression-injection.

Turning now to FIG. 53D, the transparent layer 2101 a has been polishedto remove a portion of the transparent layer 2101 a such that thesurface 2105 of transparent layer 2101 a disposed opposite the backinglayer 8003 is moved closer toward the backing layer 8003. As shown, thepolished transparent layer 2101 a, has a planar surface 2105 disposedparallel to the lower surface 8006 of the backing layer and an opposingslanted surface 2103 (that is, slanted relative to the planar surface2105). After polishing, the planar surface 2105 and the slanted surface2103 can meet along a peripheral edge 2109 and define a taper angle αtherebetween. In some implementations, the planar surface 2105 and theslanted surface 2103 do not meet but instead terminate at the peripheraledge prior to actually meeting. In such implementations, the taper angleα can still be defined to be the angle of the orientation of the planarsurface 2105 with respect to the orientation of the slanted surface2103. As illustrated in FIG. 53D, because the planar surface 2105 andthe lower surface 8006 are parallel, the taper angle α matches the angleα of the backing layer 8003. In some implementations, the taper angle αcan be between, for example, about 1 degree and 15 degrees, for example,between about 2 degrees and 8 degrees.

FIG. 53E illustrates the transparent layer 2101 c with a columnar recess2106 formed near a center portion of the transparent layer 2101 c. Thecolumnar recess can be patterned and etched to form a light entrysurface 2107 near the center portion of the transparent layer 2101 c.The light entry surface 2107 can be used to inject light into thetransparent layer 2101 c as discussed above with reference to FIGS.35D-35F. In this way, the transparent layer 2101 c of FIG. 53E can beused as a light guide in an illumination device. In someimplementations, the transparent layer 2101 c can be incorporated intoan illumination device along with the backing layer 8003 and in otherimplementations, the transparent layer 2101 c can be separated from thebacking layer 8003 for use in an illumination device. In someimplementations, substrate layer 8001 and backing layer 8003 can beintegrated to form a single integrated structure.

FIG. 54 shows an example of a flow diagram illustrating a method 9000 ofmanufacturing an illumination device. The method 9000 includes forming atransparent structure including a tapered upper surface and a lowersurface, as shown in block 9001. In some implementations, at least aportion of the upper surface can be a reflective surface or the uppersurface may be reflectorized after method 9000 is completed. In someimplementations, the transparent structure can be formed by placing atransparent material over a substrate layer and backing layer as shownand described in FIGS. 53A-53E. In some implementations, the substratelayer and backing layer can be integrated and form a single structure.As shown in block 9003, the method 9000 also includes polishing thelower surface of the transparent structure to reduce a longitudinaldimension between the lower surface and the upper surface. In someimplementations, the transparent structure can be polished to reduce thelongitudinal dimension between the lower surface and the upper surfaceto a value between 2 mm and 6 mm, for example. In some implementations,polishing the lower surface can result in the formation of a peripheraledge between the lower surface and the upper surface and a taper angledefined between the lower surface and the upper surface. The taper anglecan range between about 1 degree and 15 degrees, for example, betweenabout 2 degrees and 8 degrees.

In some implementations, the method 9000 can include forming a lightentry surface in a center portion of the transparent structure. Thelight entry surface can be defined by a recess, for example. In someimplementations, the method 9000 can also include positioning a lightsource near the center portion of the transparent structure. In thisway, light emitted from the light source can be received into thetransparent structure through the light entry surface and propagate in aradial direction from the light source toward the upper surface of thetransparent structure. Thus, the method 9000 can be utilized to formmany of the illumination devices disclosed herein where a thin taperedwaveguide can be useful, especially when the dimensions of the waveguideare such that injection molding techniques make it difficult to form anedge with a very low taper angle. In such a case, a transparent layer2101 a can be formed by, for example, injection molding, and thetransparent layer 2012 a can then be polished down to form the waveguidewith the desired edge profile.

The various illustrative logics, logical blocks, modules, circuits andalgorithm steps described in connection with the implementationsdisclosed herein may be implemented as electronic hardware, computersoftware, or combinations of both. The interchangeability of hardwareand software has been described generally, in terms of functionality,and illustrated in the various illustrative components, blocks, modules,circuits and steps described above. Whether such functionality isimplemented in hardware or software depends upon the particularapplication and design constraints imposed on the overall system.

The hardware and data processing apparatus used to implement the variousillustrative logics, logical blocks, modules and circuits described inconnection with the aspects disclosed herein may be implemented orperformed with a general purpose single- or multi-chip processor, adigital signal processor (DSP), an application specific integratedcircuit (ASIC), a field programmable gate array (FPGA) or otherprogrammable logic device, discrete gate or transistor logic, discretehardware components, or any combination thereof designed to perform thefunctions described herein. A general purpose processor may be amicroprocessor, or, any conventional processor, controller,microcontroller, or state machine. A processor may also be implementedas a combination of computing devices, e.g., a combination of a DSP anda microprocessor, a plurality of microprocessors, one or moremicroprocessors in conjunction with a DSP core, or any other suchconfiguration. In some implementations, particular steps and methods maybe performed by circuitry that is specific to a given function.

In one or more aspects, the functions described may be implemented inhardware, digital electronic circuitry, computer software, firmware,including the structures disclosed in this specification and theirstructural equivalents thereof, or in any combination thereof.Implementations of the subject matter described in this specificationalso can be implemented as one or more computer programs, i.e., one ormore modules of computer program instructions, encoded on a computerstorage media for execution by, or to control the operation of, dataprocessing apparatus.

Various modifications to the implementations described in thisdisclosure may be readily apparent to those skilled in the art, and thegeneric principles defined herein may be applied to otherimplementations without departing from the spirit or scope of thisdisclosure. Thus, the claims are not intended to be limited to theimplementations shown herein, but are to be accorded the widest scopeconsistent with this disclosure, the principles and the novel featuresdisclosed herein. The word “exemplary” is used exclusively herein tomean “serving as an example, instance, or illustration.” Anyimplementation described herein as “exemplary” is not necessarily to beconstrued as preferred or advantageous over other implementations.Additionally, a person having ordinary skill in the art will readilyappreciate, the terms “upper” and “lower” are sometimes used for ease ofdescribing the figures, and indicate relative positions corresponding tothe orientation of the figure on a properly oriented page, and may notreflect the proper orientation of the IMOD as implemented.

Certain features that are described in this specification in the contextof separate implementations also can be implemented in combination in asingle implementation. Conversely, various features that are describedin the context of a single implementation also can be implemented inmultiple implementations separately or in any suitable subcombination.Moreover, although features may be described above as acting in certaincombinations and even initially claimed as such, one or more featuresfrom a claimed combination can in some cases be excised from thecombination, and the claimed combination may be directed to asubcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. Further, the drawings may schematically depict one more exampleprocesses in the form of a flow diagram. However, other operations thatare not depicted can be incorporated in the example processes that areschematically illustrated. For example, one or more additionaloperations can be performed before, after, simultaneously, or betweenany of the illustrated operations. In certain circumstances,multitasking and parallel processing may be advantageous. Moreover, theseparation of various system components in the implementations describedabove should not be understood as requiring such separation in allimplementations, and it should be understood that the described programcomponents and systems can generally be integrated together in a singlesoftware product or packaged into multiple software products.Additionally, other implementations are within the scope of thefollowing claims. In some cases, the actions recited in the claims canbe performed in a different order and still achieve desirable results.

What is claimed is:
 1. An illumination device, comprising: a lightsource; a tapered light guide including a light input surface on an endof the light guide, a light output surface extending away from the lightinput surface along a plane at an angle to the light input surface, andan inclined surface opposite the light output surface, the inclinedsurface being at an angle α, with respect to the light output surface,of less than 15 degrees, the light source and the tapered light guidealigned such that light emitted from the light source propagates intothe light guide through the input edge surface and exits the light guidethrough the light output surface; an optical layer coupled to the lightoutput surface of the light guide, the optical layer including at leastone light redirecting element; and a light reflecting layer adjacent tothe inclined surface such that the inclined surface is located betweenthe light reflecting surface and the light output surface, wherein thelight reflecting layer is configured to reflect the light emitted fromthe light source towards the light output surface into the tapered lightguide.
 2. The illumination device of claim 1, wherein the lightreflecting layer is spaced apart from the inclined surface by a gap. 3.The illumination device of claim 2, wherein the gap includes air.
 4. Theillumination device of claim 2, wherein the gap includes a dielectric.5. The illumination device of claim 2, wherein the gap includes amaterial having an index of refraction that is less than an index ofrefraction of the light guide.
 6. The illumination device of claim 1,wherein, light exiting the light guide through the light output surfaceis collimated and the optical layer is configured to redirect lightexiting the light output surface along a desired direction.
 7. Theillumination device of claim 1, further comprising a light couplingsystem between the light source and the light input surface.
 8. Theillumination device of claim 7, wherein the light coupling systemincludes an angle transforming reflector.
 9. The illumination device ofclaim 7, wherein the light coupling system includes an etenduepreserving reflector.
 10. The illumination device of claim 7, whereinthe light coupling system includes a curved reflector.
 11. Theillumination device of claim 7, wherein the light coupling systemincludes a light guiding pipe.
 12. The device of claim 1, wherein thelight source includes one or more light emitting diodes (LEDs).
 13. Thedevice of claim 1, wherein the light source includes an array of LEDs.14. A method of manufacturing an illumination device, the methodcomprising: providing a light source; providing a tapered light guideincluding a light input surface on an end of the light guide, a lightoutput surface extending away from the light input surface along a planeat an angle to the light input surface, the light guide configured suchthat light propagating in the light guide exits through the light outputsurface; and an inclined surface opposite the light output surface, theinclined surface being at an angle α with respect to the light outputsurface of less than 15 degrees; aligning the light source and thetapered light guide such that light emitted from the light sourcepropagates into the light guide through the input edge surface; couplingan optical layer to the light output surface of the light guide, theoptical layer including at least one light redirecting element; andproviding a light reflecting layer adjacent the inclined surface,wherein the light reflecting layer is configured to reflect the lightemitted from the light source to the light output surface into thetapered light guide.
 15. The method of claim 14, further comprisingproviding a light coupling system between the light source and the lightinput surface.
 16. The method of claim 15, wherein the light couplingsystem includes an angle transforming reflector.
 17. The method of claim15, wherein the light coupling system includes an etendue preservingreflector.
 18. The method of claim 15, wherein the light coupling systemincludes a curved reflector.
 19. The method of claim 14, wherein thelight source includes one or more light emitting diodes (LEDs).
 20. Themethod of claim 14, wherein the light reflecting layer is spaced apartfrom the inclined surface by a gap.
 21. The device of claim 1, whereinthe light reflecting layer is parallel to the inclined surface.